View source for Bernoulli number

{{Short description|Rational number sequence}}
{{Use American English|date = March 2019}}
{{Use shortened footnotes|date=April 2021}}
{| class=wikitable style="text-align: right; float:right; clear:right; margin-left:1em;"
|+ Bernoulli numbers {{math|''B''{{su|p=±|b=''n''}}}}
|- 
! {{mvar|n}} !! fraction !! decimal
|- decimal
| 0 || 1 || +1.000000000 
|-
| 1 || ±{{sfrac|1|2}} || ±0.500000000
|-
| 2 || {{sfrac|1|6}} || +0.166666666
|- style="background:#ABE"
| 3 || 0 || +0.000000000
|-
| 4 || −{{sfrac|1|30}} || −0.033333333
|- style="background:#ABE"
| 5 || 0 || +0.000000000
|-
| 6 || {{sfrac|1|42}} || +0.023809523
|- style="background:#ABE"
| 7 || 0 || +0.000000000
|-
| 8 || −{{sfrac|1|30}} || −0.033333333
|- style="background:#ABE"
| 9 || 0 || +0.000000000
|-
| 10 || {{sfrac|5|66}} || +0.075757575
|- style="background:#ABE"
| 11 || 0 || +0.000000000
|-
| 12 || −{{sfrac|691|2730}} || −0.253113553
|- style="background:#ABE"
| 13 || 0 || +0.000000000
|-
| 14 || {{sfrac|7|6}} || +1.166666666
|- style="background:#ABE"
| 15 || 0 || +0.000000000
|-
| 16 || −{{sfrac|3617|510}} || −7.092156862
|- style="background:#ABE"
| 17 || 0 || +0.000000000
|-
| 18 || {{sfrac|43867|798}} || +54.97117794
|- style="background:#ABE"
| 19 || 0 || +0.000000000
|-
| 20 || −{{sfrac|174611|330}} || −529.1242424
|}

In [[mathematics]], the '''Bernoulli numbers''' {{math|''B''<sub>''n''</sub>}} are a [[sequence]] of [[rational number]]s which occur frequently in [[Mathematical analysis|analysis]]. The Bernoulli numbers appear in (and can be defined by) the [[Taylor series]] expansions of the [[tangent function|tangent]] and [[Hyperbolic function|hyperbolic tangent]] functions, in [[Faulhaber's formula]] for the sum of ''m''-th powers of the first ''n'' positive integers, in the [[Euler–Maclaurin formula]], and in expressions for certain values of the [[Riemann zeta function]].

The values of the first 20 Bernoulli numbers are given in the adjacent table. Two conventions are used in the literature, denoted here by <math>B^{-{}}_n</math> and <math>B^{+{}}_n</math>; they differ only for {{math|''n'' {{=}} 1}}, where <math>B^{-{}}_1=-1/2</math> and <math>B^{+{}}_1=+1/2</math>. For every odd {{math|''n'' > 1}}, {{math|''B''<sub>''n''</sub> {{=}} 0}}. For every even {{math|''n'' > 0}}, {{math|''B''<sub>''n''</sub>}} is negative if {{math|''n''}} is divisible by 4 and positive otherwise. The Bernoulli numbers are special values of the [[Bernoulli polynomials]] <math>B_n(x)</math>, with <math>B^{-{}}_n=B_n(0)</math> and <math>B^+_n=B_n(1)</math>.{{r|Weisstein2016}}

The Bernoulli numbers were discovered around the same time by the Swiss mathematician [[Jacob Bernoulli]], after whom they are named, and independently by Japanese mathematician [[Seki Takakazu]].  Seki's discovery was posthumously published in 1712{{r|Selin1997_891|SmithMikami1914_108|Kitagawa}} in his work ''Katsuyō Sanpō''; Bernoulli's, also posthumously, in his ''[[Ars Conjectandi]]'' of 1713.  [[Ada Lovelace]]'s [[note G]] on the [[Analytical Engine]] from 1842 describes an [[algorithm]] for generating Bernoulli numbers with [[Charles Babbage|Babbage]]'s machine;{{r|Menabrea1842_noteG}} it is disputed [[Ada Lovelace#Controversy over contribution|whether Lovelace or Babbage developed the algorithm]]. As a result, the Bernoulli numbers have the distinction of being the subject of the first published complex [[computer program]].

==Notation==
The superscript {{math|±}} used in this article distinguishes the two sign conventions for Bernoulli numbers. Only the {{math|''n'' {{=}} 1}} term is affected: 
* {{math|''B''{{su|p=−|b=''n''}} }} with {{math|''B''{{su|p=−|b=1}} {{=}}  −{{sfrac|1|2}} }} ({{OEIS2C|id=A027641}} / {{OEIS2C|id=A027642}}) is the sign convention prescribed by [[NIST]] and most modern textbooks.{{sfnp|Arfken|1970|p=278}}
* {{math|''B''{{su|p=+|b=''n''}}}} with {{math|''B''{{su|p=+|b=1}} {{=}} +{{sfrac|1|2}} }} ({{OEIS2C|id=A164555}} / {{OEIS2C|id=A027642}}) was used in the older literature,{{r|Weisstein2016}} and (since 2022) by [[Donald Knuth]]<ref>[[Donald Knuth]] (2022), [https://www-cs-faculty.stanford.edu/~knuth/news22.html Recent News (2022): Concrete Mathematics and Bernoulli]. {{blockquote|But last year I took a close look at Peter Luschny's Bernoulli manifesto, where he gives more than a dozen good reasons why the value of $B_1$ should really be plus one-half. He explains that some mathematicians of the early 20th century had unilaterally changed the conventions, because some of their formulas came out a bit nicer when the negative value was used. It was their well-intentioned but ultimately poor choice that had led to what I'd been taught in the 1950s. […]  By now, hundreds of books that use the “minus-one-half” convention have unfortunately been written. Even worse, all the major software systems for symbolic mathematics have that 20th-century aberration deeply embedded. Yet Luschny convinced me that we have all been wrong, and that it's high time to change back to the correct definition before the situation gets even worse.
}}</ref> following Peter Luschny's "Bernoulli Manifesto".<ref>Peter Luschny (2013), [http://luschny.de/math/zeta/The-Bernoulli-Manifesto.html The Bernoulli Manifesto]</ref>

In the formulas below, one can switch from one sign convention to the other with the relation <math>B_n^{+}=(-1)^n B_n^{-}</math>, or for integer {{mvar|n}} = 2 or greater, simply ignore it.

Since {{math|''B''{{sub|''n''}} {{=}} 0}} for all odd {{math|''n'' > 1}}, and many formulas only involve even-index Bernoulli numbers, a few authors write "{{math|''B''{{sub|''n''}}}}" instead of {{math|''B''{{sub|2''n''}}&nbsp;}}. This article does not follow that notation.

==History==
=== Early history ===
The Bernoulli numbers are rooted in the early history of the computation of sums of integer powers, which have been of interest to mathematicians since antiquity.

[[File:Seki Kowa Katsuyo Sampo Bernoulli numbers.png|thumb|right|A page from Seki Takakazu's ''Katsuyō Sanpō'' (1712), tabulating binomial coefficients and Bernoulli numbers]]

Methods to calculate the sum of the first {{mvar|n}} positive integers, the sum of the squares and of the cubes of the first {{mvar|n}} positive integers were known, but there were no real 'formulas', only descriptions given entirely in words. Among the great mathematicians of antiquity to consider this problem were [[Pythagoras]] (c. 572–497&nbsp;BCE, Greece), [[Archimedes]] (287–212&nbsp;BCE, Italy), [[Aryabhata]] (b. 476, India), [[Abu Bakr al-Karaji]] (d. 1019, Persia) and Abu Ali al-Hasan ibn al-Hasan ibn [[al-Haytham]] (965–1039, Iraq).

During the late sixteenth and early seventeenth centuries mathematicians made significant progress.  In the West [[Thomas Harriot]] (1560–1621) of England, [[Johann Faulhaber]] (1580–1635) of Germany, [[Pierre de Fermat]] (1601–1665) and fellow French mathematician [[Blaise Pascal]] (1623–1662) all played important roles.

Thomas Harriot seems to have been the first to derive and write formulas for sums of powers using symbolic notation, but even he calculated only up to the sum of the fourth powers.  Johann Faulhaber gave formulas for sums of powers up to the 17th power in his 1631 ''Academia Algebrae'', far higher than anyone before him, but he did not give a general formula.

Blaise Pascal in 1654 proved [[Faulhaber's formula|''Pascal's identity'']] relating the sums of the {{math|''p''}}th powers of the first {{math|''n''}} positive integers for {{math|''p'' {{=}} 0, 1, 2, ..., ''k''}}.

The Swiss mathematician Jakob Bernoulli (1654–1705) was the first to realize the existence of a single sequence of constants {{math|''B''<sub>0</sub>, ''B''<sub>1</sub>, ''B''<sub>2</sub>,...}} which provide a uniform formula for all sums of powers.{{sfnp|Knuth|1993}}

The joy Bernoulli experienced when he hit upon the pattern needed to compute quickly and easily the coefficients of his formula for the sum of the {{mvar|c}}th powers for any positive integer {{math|''c''}} can be seen from his comment. He wrote:

:"With the help of this table, it took me less than half of a quarter of an hour to find that the tenth powers of the first 1000 numbers being added together will yield the sum 91,409,924,241,424,243,424,241,924,242,500."

Bernoulli's result was published posthumously in ''[[Ars Conjectandi]]'' in 1713.  [[Seki Takakazu]] independently discovered the Bernoulli numbers and his result was published a year earlier, also posthumously, in 1712.{{r|Selin1997_891}} However, Seki did not present his method as a formula based on a sequence of constants.

Bernoulli's formula for sums of powers is the most useful and generalizable formulation to date. The coefficients in Bernoulli's formula are now called Bernoulli numbers, following a suggestion of [[Abraham de Moivre]].

Bernoulli's formula is sometimes called [[Faulhaber's formula]] after Johann Faulhaber who found remarkable ways to calculate sum of powers but never stated Bernoulli's formula. According to Knuth{{sfnp|Knuth|1993}} a rigorous proof of Faulhaber's formula was first published by [[Carl Gustav Jacob Jacobi|Carl Jacobi]] in 1834.{{r|Jacobi1834}} Knuth's in-depth study of Faulhaber's formula concludes (the nonstandard notation on the LHS is explained further on):

:''"Faulhaber never discovered the Bernoulli numbers; i.e., he never realized that a single sequence of constants'' {{math|''B''<sub>0</sub>, ''B''<sub>1</sub>, ''B''<sub>2</sub>,}} ''... would provide a uniform''
::<math display=inline>\sum n^m = \frac 1{m+1}\left( B_0n^{m+1}-\binom{m+1} 1 B_1 n^m+\binom{m+1} 2B_2n^{m-1}-\cdots +(-1)^m\binom{m+1}mB_mn\right) </math>
:''for all sums of powers. He never mentioned, for example, the fact that almost half of the coefficients turned out to be zero after he had converted his formulas for'' {{math|Σ ''n<sup>m</sup>''}} ''from polynomials in {{mvar|N}} to polynomials in {{mvar|n}}."{{sfnp|Knuth|1993|p=14}}''

In the above Knuth meant <math>B_1^-</math>; instead using <math>B_1^+</math> the formula avoids subtraction:
:<math display=inline> \sum n^m = \frac 1{m+1}\left( B_0n^{m+1}+\binom{m+1} 1 B^+_1 n^m+\binom{m+1} 2B_2n^{m-1}+\cdots+\binom{m+1}mB_mn\right). </math>

=== Reconstruction of "Summae Potestatum" ===
[[File:JakobBernoulliSummaePotestatum.png|thumb|right|upright=1.5|Jakob Bernoulli's "Summae Potestatum", 1713{{efn|Translation of the text: 
" ... And if [one were] to proceed onward step by step to higher powers, one may furnish, with little difficulty, the following list:<br>
Sums of powers<br>
<math>\textstyle \int n = \sum_{k=1}^n k = \frac {1}{2} n^2 + \frac {1}{2} n </math><br>
::::⋮
<math>\textstyle \int n^{10} = \sum_{k=1}^n k^{10} = \frac {1}{11} n^{11} + \frac {1}{2} n^{10} + \frac {5}{6} n^9 - 1 n^7 + 1 n^5 - \frac {1}{2} n^3 + \frac {5}{66} n </math><br>
Indeed [if] one will have examined diligently the law of arithmetic progression there, one will also be able to continue the same without these circuitous computations:  For [if] <math>\textstyle c </math> is taken as the exponent of any power, the sum of all <math>\textstyle n^c </math> is produced or<br>
<math>\textstyle \int n^c = \sum_{k=1}^n k^c = \frac {1}{c+1} n^{c+1} + \frac {1}{2} n^c + \frac {c}{2} An^{c-1} + \frac {c(c-1)(c-2)}{2\cdot 3\cdot4} Bn^{c-3} + \frac {c(c-1)(c-2)(c-3)(c-4)}{2\cdot 3\cdot 4 \cdot 5 \cdot 6} Cn^{c-5} + \frac {c(c-1)(c-2)(c-3)(c-4)(c-5)(c-6)}{2\cdot 3\cdot 4 \cdot 5 \cdot 6 \cdot 7  \cdot 8} Dn^{c-7} + \cdots </math><br>
and so forth, the exponent of its power <math>n</math> continually diminishing by 2 until it arrives at <math>n</math> or <math>n^2</math>.  The capital letters <math>\textstyle  A, B, C, D, </math> etc. denote in order the coefficients of the last terms for <math>\textstyle \int n^2 , \int n^4 , \int n^6 , \int n^8 </math>, etc. namely<br>
<math>\textstyle  A = \frac {1}{6} , B = - \frac {1}{30} , C = \frac {1}{42} , D = - \frac {1}{30} </math>."<br>
[Note:  The text of the illustration contains some typos:  ''ensperexit'' should read ''inspexerit'', ''ambabimus'' should read ''ambagibus'', ''quosque'' should read ''quousque'', and in Bernoulli's original text ''Sumtâ'' should read ''Sumptâ'' or ''Sumptam''.]
* {{citation |last=Smith |first=David Eugene |date= 1929 |chapter=Jacques (I) Bernoulli: On the 'Bernoulli Numbers' |title= A Source Book in Mathematics |chapter-url=https://archive.org/details/sourcebookinmath00smit/page/85 |location=New York |publisher=McGraw-Hill Book Co. |pages=85–90 }}
* {{citation |last=Bernoulli |first=Jacob |date=1713 |title=Ars Conjectandi |url=https://archive.org/details/jacobibernoulli00bern/page/97 |location=Basel |publisher=Impensis Thurnisiorum, Fratrum |pages=97–98 |language=la |doi=10.5479/sil.262971.39088000323931}}
}}]]

The Bernoulli numbers {{OEIS2C|id=A164555}}(n)/{{OEIS2C|id=A027642}}(n) were introduced by Jakob Bernoulli in the book ''[[Ars Conjectandi]]'' published posthumously in 1713 page 97. The main formula can be seen in the second half of the corresponding facsimile. The constant coefficients denoted {{math|''A''}}, {{math|''B''}}, {{math|''C''}} and {{math|''D''}} by Bernoulli are mapped to the notation which is now prevalent as {{math|''A'' {{=}} ''B''<sub>2</sub>}}, {{math|''B'' {{=}} ''B''<sub>4</sub>}}, {{math|''C'' {{=}} ''B''<sub>6</sub>}}, {{math|''D'' {{=}} ''B''<sub>8</sub>}}. The expression {{math|''c''·''c''−1·''c''−2·''c''−3}} means {{math|''c''·(''c''−1)·(''c''−2)·(''c''−3)}} – the small dots are used as grouping symbols. Using today's terminology these expressions are [[Pochhammer symbol|falling factorial powers]] {{math|''c''<sup>{{underline|''k''}}</sup>}}. The factorial notation {{math|''k''!}} as a shortcut for {{math|1 × 2 × ... × ''k''}} was not introduced until 100 years later. The integral symbol on the left hand side goes back to [[Gottfried Wilhelm Leibniz]] in 1675 who used it as a long letter {{math|''S''}} for "summa" (sum).{{efn|The {{harvp|''Mathematics Genealogy Project''|n.d.}} shows Leibniz as the academic<!--not doctoral--> advisor of Jakob Bernoulli. See also {{harvp|Miller|2017}}.}} The letter {{math|''n''}} on the left hand side is not an index of [[summation]] but gives the upper limit of the range of summation which is to be understood as {{math|1, 2, ..., ''n''}}. Putting things together, for positive {{math|''c''}}, today a mathematician is likely to write Bernoulli's formula as:

: <math> \sum_{k=1}^n k^c = \frac{n^{c+1}}{c+1}+\frac 1 2 n^c+\sum_{k=2}^c \frac{B_k}{k!} c^{\underline{k-1}}n^{c-k+1}.</math>

This formula suggests setting {{math|''B''<sub>1</sub> {{=}} {{sfrac|1|2}}}} when switching from the so-called 'archaic' enumeration which uses only the even indices 2, 4, 6... to the modern form (more on different conventions in the next paragraph). Most striking in this context is the fact that the [[falling factorial#Real_numbers_and_negative_n|falling factorial]] {{math|''c''<sup>{{underline|''k''−1}}</sup>}} has for {{math|''k'' {{=}} 0}} the value {{math|{{sfrac|1|''c'' + 1}}}}.{{sfnp|Graham|Knuth|Patashnik|1989|loc=Section 2.51}} Thus Bernoulli's formula can be written
: <math> \sum_{k=1}^n k^c = \sum_{k=0}^c \frac{B_k}{k!}c^{\underline{k-1}} n^{c-k+1}</math>

if {{math|''B''<sub>1</sub> {{=}} 1/2}}, recapturing the value Bernoulli gave to the coefficient at that position.

The formula for <math>\textstyle \sum_{k=1}^n k^9</math> in the first half of the quotation by Bernoulli above contains an error at the last term; it should be <math>-\tfrac {3}{20}n^2</math> instead of <math>-\tfrac {1}{12}n^2</math>.

== Definitions ==
Many characterizations of the Bernoulli numbers have been found in the last 300 years, and each could be used to introduce these numbers.  Here only four of the most useful ones are mentioned:

* a recursive equation,
* an explicit formula,
* a generating function,
* an integral expression.

For the proof of the [[Logical equivalence|equivalence]] of the four approaches.<ref>See {{harvp|Ireland|Rosen|1990}} or {{harvp|Conway|Guy|1996}}.</ref>

=== Recursive definition ===
The Bernoulli numbers obey the sum formulas{{r|Weisstein2016}}
: <math> \begin{align} \sum_{k=0}^{m}\binom {m+1} k B^{-{}}_k &= \delta_{m, 0} \\ \sum_{k=0}^{m}\binom {m+1} k B^{+{}}_k &= m+1 \end{align}</math>
where <math>m=0,1,2...</math> and {{math|''δ''}} denotes the [[Kronecker delta]]. Solving for <math>B^{\mp{}}_m</math> gives the recursive formulas
: <math>\begin{align}
  B_m^{-{}} &= \delta_{m, 0} - \sum_{k=0}^{m-1} \binom{m}{k} \frac{B^{-{}}_k}{m - k + 1} \\
  B_m^+ &= 1 - \sum_{k=0}^{m-1} \binom{m}{k} \frac{B^+_k}{m - k + 1}.
\end{align}</math>

=== Explicit definition ===
In 1893 [[Louis Saalschütz]] listed  a total of 38 explicit formulas for the Bernoulli numbers,{{r|Saalschütz1893}} usually giving some reference in the older literature. One of them is (for <math>m\geq 1</math>):
:<math>\begin{align}
  B^-_m &= \sum_{k=0}^m \frac1{k+1} \sum_{j=0}^k \binom{k}{j} (-1)^j j^m \\
  B^+_m &= \sum_{k=0}^m \frac1{k+1} \sum_{j=0}^k \binom{k}{j} (-1)^j  (j + 1)^m.
\end{align}</math>

=== Generating function ===
The exponential [[generating function]]s are
:<math>\begin{alignat}{3}
  \frac{t}{e^t - 1}    &= \frac{t}{2} \left( \operatorname{coth} \frac{t}{2} -1 \right) &&= \sum_{m=0}^\infty \frac{B^{-{}}_m t^m}{m!}\\
  \frac{te^t}{e^t - 1} = \frac{t}{1 - e^{-t}} &= \frac{t}{2} \left( \operatorname{coth} \frac{t}{2} +1 \right) &&= \sum_{m=0}^\infty \frac{B^+_m t^m}{m!}.
\end{alignat}</math>
where the substitution is <math>t \to - t</math>. The two generating functions only differ by ''t''.
{{collapse top|title=Proof}}
If we let <math>F(t)=\sum_{i=1}^\infty f_it^i</math> and <math>G(t)=1/(1+F(t))=\sum_{i=0}^\infty g_it^i</math> then

:<math>G(t)=1-F(t)G(t).</math>

Then <math>g_0=1</math> and for <math>m>0</math> the m{{sup|th}} term in the series for <math>G(t)</math> is:

:<math>g_mt^i=-\sum_{j=0}^{m-1}f_{m-j}g_jt^m</math>

If

:<math>F(t)=\frac{e^t-1}t-1=\sum_{i=1}^\infty \frac{t^i}{(i+1)!}</math>

then we find that

:<math>G(t)=t/(e^t-1)</math>

:<math>\begin{align}
m!g_m&=-\sum_{j=0}^{m-1}\frac{m!}{j!}\frac{j!g_j}{(m-j+1)!}\\
&=-\frac 1{m+1}\sum_{j=0}^{m-1}\binom{m+1}jj!g_j\\
\end{align}</math>

showing that the values of <math>i!g_i</math> obey the recursive formula for the Bernoulli numbers <math>B^-_i</math>.
{{collapse bottom}}

The (ordinary) generating function
: <math> z^{-1} \psi_1(z^{-1}) = \sum_{m=0}^{\infty} B^+_m z^m</math>

is an [[asymptotic series]]. It contains the [[trigamma function]] {{math|''ψ''<sub>1</sub>}}.

=== Integral Expression ===
From the generating functions above, one can obtain the following integral formula for the even Bernoulli numbers: 

:<math>B_{2n} = 4n (-1)^{n+1} \int_0^{\infty} \frac{t^{2n-1}}{e^{2 \pi t} -1 } \mathrm{d} t </math>

== Bernoulli numbers and the Riemann zeta function ==

[[File:BernoulliNumbersByZeta.svg|thumb|right|The Bernoulli numbers as given by the Riemann zeta function.]]

The Bernoulli numbers can be expressed in terms of the [[Riemann zeta function]]:

:{{math|1=''B''{{su|p=+|b=''n''}} = −''n ζ''(1 − ''n'')}} &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; for {{math|''n'' ≥ 1}}&nbsp;.

Here the argument of the zeta function is ''0 ''or negative. As <math>\zeta(k)</math> is zero for negative even integers (the [[Riemann_zeta_function#Zeros,_the_critical_line,_and_the_Riemann_hypothesis|trivial zeroes]]), if ''n>1'' is odd, <math>\zeta(1-n)</math> is zero.

By means of the zeta [[Riemann zeta function#Riemann's functional equation|functional equation]] and the gamma [[Gamma function#General|reflection formula]] the following relation can be obtained:{{sfnp|Arfken|1970|p=279}}

:<math> B_{2n} = \frac {(-1)^{n+1}2(2n)!} {(2\pi)^{2n}} \zeta(2n) \quad </math> for {{math|''n'' ≥ 1}}&nbsp;.

Now the argument of the zeta function is positive.

It then follows from {{math|''&zeta;'' &rarr; 1}} ({{math|''n'' &rarr; &infin;}}) and [[Stirling formula|Stirling's formula]] that
: <math> |B_{2 n}| \sim 4 \sqrt{\pi n} \left(\frac{n}{ \pi e} \right)^{2n} \quad </math> for {{math|''n'' &rarr; &infin;}}&nbsp;.

== Efficient computation of Bernoulli numbers ==

In some applications it is useful to be able to compute the Bernoulli numbers {{math|''B''<sub>0</sub>}} through {{math|''B''<sub>''p'' − 3</sub>}} modulo {{mvar|p}}, where {{mvar|p}} is a prime; for example to test whether [[Vandiver's conjecture]] holds for {{mvar|p}}, or even just to determine whether {{mvar|p}} is an [[irregular prime]]. It is not feasible to carry out such a computation using the above recursive formulae, since at least (a constant multiple of) {{math|''p''<sup>2</sup>}} arithmetic operations would be required. Fortunately, faster methods have been developed{{r|BuhlerCraErnMetShokrollahi2001}} which require only {{math|''O''(''p'' (log ''p'')<sup>2</sup>)}} operations (see [[big-O notation|big {{mvar|O}} notation]]).

David Harvey{{r|Harvey2010}} describes an algorithm for computing Bernoulli numbers by computing {{math|''B''<sub>''n''</sub>}} modulo {{mvar|p}} for many small primes {{mvar|p}}, and then reconstructing {{math|''B''<sub>''n''</sub>}} via the [[Chinese remainder theorem]]. Harvey writes that the [[Asymptotic analysis|asymptotic]] [[Computational complexity theory|time complexity]] of this algorithm is {{math|''O''(''n''<sup>2</sup> log(''n'')<sup>2 + ''ε''</sup>)}} and claims that this [[implementation]] is significantly faster than implementations based on other methods. Using this implementation Harvey computed {{math|''B''<sub>''n''</sub>}} for {{math|''n'' {{=}} 10<sup>8</sup>}}. Harvey's implementation has been included in [[SageMath]] since version 3.1. Prior to that, Bernd Kellner{{r|Kellner2002}}<!--A more specific citation would be preferable.--> computed {{math|''B''<sub>''n''</sub>}} to full precision for {{math|''n'' {{=}} 10<sup>6</sup>}} in December 2002 and Oleksandr Pavlyk{{r|Pavlyk29Apr2008}} for {{math|''n'' {{=}} 10<sup>7</sup>}} with [[Mathematica]] in April 2008.

{{table alignment}}
:{| class="wikitable defaultright col1left"
! Computer !! Year !! ''n'' !! Digits*
|-
| J. Bernoulli || ~1689 || 10 || 1
|-
| L. Euler || 1748 || 30 || 8
|- 
| J. C. Adams || 1878 || 62 || 36
|- 
| D. E. Knuth, T. J. Buckholtz || 1967 || {{val|1672|fmt=gaps}} || {{val|3330|fmt=gaps}}
|- 
| G. Fee, [[S. Plouffe]] || 1996 || {{val|10000}} || {{val|27677}}
|- 
| G. Fee, S. Plouffe || 1996 || {{val|100000}} || {{val|376755}}
|- 
| B. C. Kellner || 2002 || {{val|1000000}} || {{val|4767529}}
|- 
| O. Pavlyk || 2008 || {{val|10000000}} || {{val|57675260}}
|- 
| D. Harvey || 2008 || {{val|100000000}} || {{val|676752569}}
|}
::<nowiki>*</nowiki> ''Digits'' is to be understood as the exponent of 10 when {{math|''B''<sub>''n''</sub>}} is written as a real number in normalized [[scientific notation]].

== Applications of the Bernoulli numbers ==

=== Asymptotic analysis ===
Arguably the most important application of the Bernoulli numbers in mathematics is their use in the [[Euler–Maclaurin formula]]. Assuming that {{mvar|f}} is a sufficiently often differentiable function the Euler–Maclaurin formula can be written as{{sfnp|Graham|Knuth|Patashnik|1989|loc=9.67}}

: <math>\sum_{k=a}^{b-1} f(k) = \int_a^b f(x)\,dx + \sum_{k=1}^m \frac{B^-_k}{k!} (f^{(k-1)}(b)-f^{(k-1)}(a))+R_-(f,m).</math>

This formulation assumes the convention {{math|1=''B''{{su|p=−|b=1}} = −{{sfrac|1|2}}}}. Using the convention {{math|1=''B''{{su|p=+|b=1}} = +{{sfrac|1|2}}}} the formula becomes

: <math>\sum_{k=a+1}^{b} f(k) = \int_a^b f(x)\,dx + \sum_{k=1}^m \frac{B^+_k}{k!} (f^{(k-1)}(b)-f^{(k-1)}(a))+R_+(f,m).</math>

Here <math>f^{(0)}=f</math> (i.e. the zeroth-order derivative of <math>f</math> is just <math>f</math>). Moreover, let <math>f^{(-1)}</math> denote an [[antiderivative]] of <math>f</math>. By the [[fundamental theorem of calculus]],

: <math>\int_a^b f(x)\,dx = f^{(-1)}(b) - f^{(-1)}(a).</math>

Thus the last formula can be further simplified to the following succinct form of the Euler–Maclaurin formula

: <math> \sum_{k=a+1}^{b} f(k)= \sum_{k=0}^m \frac{B_k}{k!} (f^{(k-1)}(b)-f^{(k-1)}(a))+R(f,m). </math>

This form is for example the source for the important Euler–Maclaurin expansion of the zeta function

: <math> \begin{align}
  \zeta(s) & =\sum_{k=0}^m \frac{B^+_k}{k!} s^{\overline{k-1}} + R(s,m) \\
           & = \frac{B_0}{0!}s^{\overline{-1}} + \frac{B^+_1}{1!} s^{\overline{0}} + \frac{B_2}{2!} s^{\overline{1}} +\cdots+R(s,m) \\
           & = \frac{1}{s-1} + \frac{1}{2} + \frac{1}{12}s + \cdots + R(s,m).
\end{align} </math>

Here {{math|''s''<sup>{{overline|''k''}}</sup>}} denotes the [[Pochhammer symbol|rising factorial power]].{{sfnp|Graham|Knuth|Patashnik|1989|loc=2.44, 2.52}}

Bernoulli numbers are also frequently used in other kinds of [[asymptotic expansion]]s. The following example is the classical Poincaré-type asymptotic expansion of the [[digamma function]] {{math|''ψ''}}.

:<math>\psi(z) \sim \ln z - \sum_{k=1}^\infty \frac{B^+_k}{k z^k} </math>

=== Sum of powers ===
{{main|Faulhaber's formula}}
Bernoulli numbers feature prominently in the [[Closed-form expression|closed form]] expression of the sum of the {{math|''m''}}th powers of the first {{math|''n''}} positive integers. For {{math|''m'', ''n'' ≥ 0}} define

:<math>S_m(n) = \sum_{k=1}^n k^m = 1^m + 2^m + \cdots + n^m. </math>

This expression can always be rewritten as a [[polynomial]] in {{math|''n''}} of degree {{math|''m'' + 1}}. The [[coefficient]]s of these polynomials are related to the Bernoulli numbers by '''Bernoulli's formula''':
: <math>S_m(n) = \frac{1}{m + 1} \sum_{k=0}^m \binom{m + 1}{k} B^+_k n^{m + 1 - k} = m! \sum_{k=0}^m \frac{B^+_k n^{m + 1 - k}}{k! (m+1-k)!} ,</math>
where {{math|<big><big>(</big></big>{{su|p=''m'' + 1|b=''k''|a=c}}<big><big>)</big></big>}} denotes the [[binomial coefficient]].

For example, taking {{math|''m''}} to be 1 gives the [[triangular number]]s {{math|0, 1, 3, 6, ...}} {{OEIS2C|id=A000217}}.

:<math> 1 + 2 + \cdots + n = \frac{1}{2} (B_0 n^2 + 2 B^+_1 n^1) = \tfrac12 (n^2 + n).</math>

Taking {{math|''m''}} to be 2 gives the [[square pyramidal number]]s {{math|0, 1, 5, 14, ...}} {{OEIS2C|id=A000330}}.

: <math>1^2 + 2^2 + \cdots + n^2 = \frac{1}{3} (B_0 n^3 + 3 B^+_1 n^2 + 3 B_2 n^1) = \tfrac13 \left(n^3 + \tfrac32 n^2 + \tfrac12 n\right).</math>

Some authors use the alternate convention for Bernoulli numbers and state Bernoulli's formula in this way:
: <math>S_m(n) = \frac{1}{m + 1} \sum_{k=0}^m (-1)^k \binom{m + 1}{k} B^{-{}}_k n^{m + 1 - k}.</math>

Bernoulli's formula is sometimes called [[Faulhaber's formula]] after [[Johann Faulhaber]] who also found remarkable ways to calculate [[sums of powers]].

Faulhaber's formula was generalized by V. Guo and J. Zeng to a [[q-analog|{{mvar|q}}-analog]].{{r|GuoZeng2005}}

===Taylor series===
The Bernoulli numbers appear in the [[Taylor series]] expansion of many [[trigonometric functions]] and [[hyperbolic function]]s.

<math display="block">\begin{align}
\tan x &= \hphantom{{1\over x}} \sum_{n=1}^\infty \frac{(-1)^{n-1} 2^{2n} (2^{2n}-1) B_{2n} }{(2n)!}\; x^{2n-1}, && \left|x \right| < \frac \pi 2. \\
\cot x &= {1\over x} \sum_{n=0}^\infty \frac{(-1)^n B_{2n} (2x)^{2n}}{(2n)!}, & 0 < & |x| < \pi. \\
\tanh x &= \hphantom{{1\over x}} \sum_{n=1}^\infty \frac{2^{2n}(2^{2n}-1)B_{2n}}{(2n)!}\;x^{2n-1}, && |x| < \frac \pi 2. \\
\coth x &= {1\over x} \sum_{n=0}^\infty \frac{B_{2n} (2x)^{2n}}{(2n)!}, & 0 < & |x| < \pi.
\end{align}</math>

===Laurent series===
The Bernoulli numbers appear in the following [[Laurent series]]:{{sfnp|Arfken|1970|p=463}}

[[Digamma function]]: <math> \psi(z)= \ln z- \sum_{k=1}^\infty \frac {B_k^{+{}}} {k z^k} </math>

=== Use in topology ===
The [[Kervaire–Milnor formula]] for the order of the cyclic group of diffeomorphism classes of [[exotic sphere|exotic {{math|(4''n'' − 1)}}-spheres]] which bound [[parallelizable manifold]]s involves Bernoulli numbers. Let {{math|''ES''<sub>''n''</sub>}} be the number of such exotic spheres for {{Math|''n'' ≥ 2}}, then

:<math>\textit{ES}_n = (2^{2n-2}-2^{4n-3}) \operatorname{Numerator}\left(\frac{B_{4n}}{4n} \right) .</math>

The [[Hirzebruch signature theorem#L genus and the Hirzebruch signature theorem|Hirzebruch signature theorem]] for the [[Hirzebruch signature theorem#L genus and the Hirzebruch signature theorem|{{mvar|L}} genus]] of a [[Smooth manifold|smooth]] [[Orientability|oriented]] [[closed manifold]] of [[dimension]] 4''n'' also involves Bernoulli numbers.

== Connections with combinatorial numbers ==
The connection of the Bernoulli number to various kinds of combinatorial numbers is based on the classical theory of finite differences and on the combinatorial interpretation of the Bernoulli numbers as an instance of a fundamental combinatorial principle, the [[inclusion–exclusion principle]].

=== Connection with Worpitzky numbers ===
The definition to proceed with was developed by Julius Worpitzky in 1883. Besides elementary arithmetic only the factorial function {{math|''n''!}} and the power function {{math|''k<sup>m</sup>''}} is employed. The signless Worpitzky numbers are defined as

: <math> W_{n,k}=\sum_{v=0}^k (-1)^{v+k} (v+1)^n \frac{k!}{v!(k-v)!} . </math>

They can also be expressed through the [[Stirling numbers of the second kind]]

: <math> W_{n,k}=k! \left\{ {n+1\atop k+1} \right\}.</math>

A Bernoulli number is then introduced as an inclusion–exclusion sum of Worpitzky numbers weighted by the [[Harmonic progression (mathematics)|harmonic sequence]] 1,&nbsp;{{sfrac|1|2}},&nbsp;{{sfrac|1|3}},&nbsp;...

: <math> B_{n}=\sum_{k=0}^n (-1)^k \frac{W_{n,k}}{k+1}\ =\ \sum_{k=0}^n \frac{1}{k+1} \sum_{v=0}^k (-1)^v (v+1)^n {k \choose v}\ . </math>

:{{math|1=''B''<sub>0</sub> = 1}}
:{{math|1=''B''<sub>1</sub> = 1 − {{sfrac|1|2}}}}
:{{math|1=''B''<sub>2</sub> = 1 − {{sfrac|3|2}} + {{sfrac|2|3}}}}
:{{math|1=''B''<sub>3</sub> = 1 − {{sfrac|7|2}} + {{sfrac|12|3}} − {{sfrac|6|4}}}}
:{{math|1=''B''<sub>4</sub> = 1 − {{sfrac|15|2}} + {{sfrac|50|3}} − {{sfrac|60|4}} + {{sfrac|24|5}}}}
:{{math|1=''B''<sub>5</sub> = 1 − {{sfrac|31|2}} + {{sfrac|180|3}} − {{sfrac|390|4}} + {{sfrac|360|5}} − {{sfrac|120|6}}}}
:{{math|1=''B''<sub>6</sub> = 1 − {{sfrac|63|2}} + {{sfrac|602|3}} − {{sfrac|2100|4}} + {{sfrac|3360|5}} − {{sfrac|2520|6}} + {{sfrac|720|7}}}}

This representation has {{math|''B''{{su|p=+|b=1}} {{=}} +{{sfrac|1|2}}}}.

Consider the sequence {{math|''s<sub>n</sub>''}}, {{math|''n'' ≥ 0}}. From Worpitzky's numbers {{OEIS2C|id=A028246}}, {{OEIS2C|id=A163626}} applied to {{math|''s''<sub>0</sub>, ''s''<sub>0</sub>, ''s''<sub>1</sub>, ''s''<sub>0</sub>, ''s''<sub>1</sub>, ''s''<sub>2</sub>, ''s''<sub>0</sub>, ''s''<sub>1</sub>, ''s''<sub>2</sub>, ''s''<sub>3</sub>, ...}} is identical to the Akiyama–Tanigawa transform applied to {{math|''s<sub>n</sub>''}} (see [[#Connection with Stirling numbers of the first kind|Connection with Stirling numbers of the first kind]]). This can be seen via the table:

:{| style="text-align:center"
|+ '''Identity of<br/>Worpitzky's representation and Akiyama–Tanigawa transform'''
|-
|1|| || || || || ||0||1|| || || || ||0||0||1|| || || ||0||0||0||1|| || ||0||0||0||0||1|| 
|-
|1||−1|| || || || ||0||2||−2|| || || ||0||0||3||−3|| || ||0||0||0||4||−4|| || || || || || || 
|-
|1||−3||2|| || || ||0||4||−10||6|| || ||0||0||9||−21||12|| || || || || || || || || || || || || 
|-
|1||−7||12||−6|| || ||0||8||−38||54||−24|| || || || || || || || || || || || || || || || || || || 
|-
|1||−15||50||−60||24|| || || || || || || || || || || || || || || || || || || || || || || || || 
|-
|}

The first row represents {{math|''s''<sub>0</sub>, ''s''<sub>1</sub>, ''s''<sub>2</sub>, ''s''<sub>3</sub>, ''s''<sub>4</sub>}}.

Hence for the second fractional Euler numbers {{OEIS2C|id=A198631}} ({{math|''n''}}) / {{OEIS2C|id=A006519}} ({{math|''n'' + 1}}):

:{{math|1= ''E''<sub>0</sub> = 1}}
:{{math|1= ''E''<sub>1</sub> = 1 − {{sfrac|1|2}}}}
:{{math|1= ''E''<sub>2</sub> = 1 − {{sfrac|3|2}} + {{sfrac|2|4}}}}
:{{math|1= ''E''<sub>3</sub> = 1 − {{sfrac|7|2}} + {{sfrac|12|4}} − {{sfrac|6|8}}}}
:{{math|1= ''E''<sub>4</sub> = 1 − {{sfrac|15|2}} + {{sfrac|50|4}} − {{sfrac|60|8}} + {{sfrac|24|16}}}}
:{{math|1= ''E''<sub>5</sub> = 1 − {{sfrac|31|2}} + {{sfrac|180|4}} − {{sfrac|390|8}} + {{sfrac|360|16}} − {{sfrac|120|32}}}}
:{{math|1= ''E''<sub>6</sub> = 1 − {{sfrac|63|2}} + {{sfrac|602|4}} − {{sfrac|2100|8}} + {{sfrac|3360|16}} − {{sfrac|2520|32}} + {{sfrac|720|64}}}}

A second formula representing the Bernoulli numbers by the Worpitzky numbers is for {{math|''n'' ≥ 1}}

: <math> B_n=\frac n {2^{n+1}-2}\sum_{k=0}^{n-1} (-2)^{-k}\, W_{n-1,k} . </math>

The simplified second Worpitzky's representation of the second Bernoulli numbers is:

{{OEIS2C|id=A164555}} ({{math|''n'' + 1}}) / {{OEIS2C|id=A027642}}({{math|''n'' + 1}}) = {{math|{{sfrac|''n'' + 1|2<sup>''n'' + 2</sup> − 2}}}} × {{OEIS2C|id=A198631}}({{math|''n''}}) / {{OEIS2C|id=A006519}}({{math|''n'' + 1}})

which links the second Bernoulli numbers to the second fractional Euler numbers. The beginning is:

:{{math|{{sfrac|1|2}}, {{sfrac|1|6}}, 0, −{{sfrac|1|30}}, 0, {{sfrac|1|42}}, ... {{=}} ({{sfrac|1|2}}, {{sfrac|1|3}}, {{sfrac|3|14}}, {{sfrac|2|15}}, {{sfrac|5|62}}, {{sfrac|1|21}}, ...) × (1, {{sfrac|1|2}}, 0, −{{sfrac|1|4}}, 0, {{sfrac|1|2}}, ...)}}

The numerators of the first parentheses are {{OEIS2C|id=A111701}} (see [[#Connection with Stirling numbers of the first kind|Connection with Stirling numbers of the first kind]]).

=== Connection with Stirling numbers of the second kind ===

If one defines the [[Bernoulli polynomials]] {{math|''B<sub>k</sub>''(''j'')}} as:{{r|Rademacher1973}}

:<math> B_k(j)=k\sum_{m=0}^{k-1}\binom{j}{m+1}S(k-1,m)m!+B_k </math>

where {{math|''B<sub>k</sub>''}} for {{math|''k'' {{=}} 0, 1, 2,...}} are the Bernoulli numbers,
and {{math|''S(k,m)''}} is a [[Stirling numbers of the second kind|Stirling number of the second kind]].

One also has the following for Bernoulli polynomials,{{r|Rademacher1973}}

:<math>  B_k(j)=\sum_{n=0}^k \binom{k}{n} B_n j^{k-n}. </math>

The coefficient of {{mvar|j}} in {{math|<big><big>(</big></big>{{su|p=''j''|b=''m'' + 1|a=c}}<big><big>)</big></big>}} is {{math|{{sfrac|(−1)<sup>''m''</sup>|''m'' + 1}}}}.

Comparing the coefficient of {{mvar|j}} in the two expressions of Bernoulli polynomials, one has:

: <math> B_k=\sum_{m=0}^{k-1} (-1)^m \frac{m!}{m+1} S(k-1,m)</math>

(resulting in {{math|''B''<sub>1</sub> {{=}} +{{sfrac|1|2}}}}) which is an explicit formula for Bernoulli numbers and can be used to prove [[Von Staudt–Clausen theorem|Von-Staudt Clausen theorem]].{{r|Boole1880|Gould1972|Apostol2010_197}}

=== Connection with Stirling numbers of the first kind ===
The two main formulas relating the unsigned [[Stirling numbers of the first kind]] {{math|<big><big>[</big></big>{{su|p=''n''|b=''m''|a=c}}<big><big>]</big></big>}} to the Bernoulli numbers (with {{math|''B''<sub>1</sub> {{=}} +{{sfrac|1|2}}}}) are

: <math> \frac{1}{m!}\sum_{k=0}^m (-1)^{k} \left[{m+1\atop k+1}\right] B_k = \frac{1}{m+1}, </math>

and the inversion of this sum (for {{math|''n'' ≥ 0}}, {{math|''m'' ≥ 0}})

: <math> \frac{1}{m!}\sum_{k=0}^m (-1)^k \left[{m+1\atop k+1}\right] B_{n+k} = A_{n,m}. </math>

Here the number {{math|''A''<sub>''n'',''m''</sub>}} are the rational Akiyama–Tanigawa numbers, the first few of which are displayed in the following table.

:{| class="wikitable" style="text-align:center"
|+ Akiyama–Tanigawa number
! {{diagonal split header|{{mvar|n}}|{{mvar|m}}}}!!0!!1!!2!!3!!4
|-
! 0 
| 1 || {{sfrac|1|2}} || {{sfrac|1|3}} || {{sfrac|1|4}} || {{sfrac|1|5}}
|-
! 1 
| {{sfrac|1|2}} || {{sfrac|1|3}} || {{sfrac|1|4}} || {{sfrac|1|5}} || ...
|-
! 2 
| {{sfrac|1|6}} || {{sfrac|1|6}} || {{sfrac|3|20}} || ... || ...
|-
! 3 
| 0 || {{sfrac|1|30}} || ... || ... || ...
|-
! 4 
| −{{sfrac|1|30}} || ... || ... || ... || ...
|}

The Akiyama–Tanigawa numbers satisfy a simple recurrence relation which can be exploited to iteratively compute the Bernoulli numbers. This leads to the algorithm shown in the section 'algorithmic description' above. See {{OEIS2C|id=A051714}}/{{OEIS2C|id=A051715}}.

An ''autosequence'' is a sequence which has its inverse binomial transform equal to the signed sequence. If the main diagonal is zeroes = {{OEIS2C|id=A000004}}, the autosequence is of the first kind. Example: {{OEIS2C|id=A000045}}, the Fibonacci numbers. If the main diagonal is the first upper diagonal multiplied by 2, it is of the second kind. Example: {{OEIS2C|id=A164555}}/{{OEIS2C|id=A027642}}, the second Bernoulli numbers (see {{OEIS2C|id=A190339}}). The Akiyama–Tanigawa transform applied to {{math|''2''<sup>−''n''</sup>}} = 1/{{OEIS2C|id=A000079}} leads to {{OEIS2C|id=A198631}} (''n'') / {{OEIS2C|id=A06519}} (''n'' + 1). Hence:

:{| class="wikitable" style="text-align:center"
|+ Akiyama–Tanigawa transform for the second Euler numbers
|-
! {{diagonal split header|{{mvar|n}}|{{mvar|m}}}} !! 0 !! 1 !! 2 !! 3 !! 4
|-
! 0
| 1 || {{sfrac|1|2}} || {{sfrac|1|4}} || {{sfrac|1|8}} || {{sfrac|1|16}}
|-
! 1 
| {{sfrac|1|2}} || {{sfrac|1|2}} || {{sfrac|3|8}} || {{sfrac|1|4}} || ...
|-
! 2 
| 0 || {{sfrac|1|4}} || {{sfrac|3|8}} || ... || ...
|-
! 3 
| −{{sfrac|1|4}} || −{{sfrac|1|4}} || ... || ... || ...
|-
! 4 
| 0 || ... || ... || ... || ...
|}

See {{OEIS2C|id=A209308}} and {{OEIS2C|id=A227577}}. {{OEIS2C|id=A198631}} ({{math|''n''}}) / {{OEIS2C|id=A006519}} ({{math|''n'' + 1}}) are the second (fractional) Euler numbers and an autosequence of the second kind.

:({{sfrac|{{OEIS2C|id=A164555}} ({{math|''n'' + 2}})|{{OEIS2C|id=A027642}} ({{math|''n'' + 2}})}} = {{math|{{sfrac|1|6}}, 0, −{{sfrac|1|30}}, 0, {{sfrac|1|42}}, ...}}) × ( {{math|{{sfrac|2<sup>''n'' + 3</sup> − 2|''n'' + 2}}}} = {{math|3, {{sfrac|14|3}}, {{sfrac|15|2}}, {{sfrac|62|5}}, 21, ...}}) = {{sfrac|{{OEIS2C|id=A198631}} ({{math|''n'' + 1}})|{{OEIS2C|id=A006519}} ({{math|''n'' + 2}})}} = {{math|{{sfrac|1|2}}, 0, −{{sfrac|1|4}}, 0, {{sfrac|1|2}}, ...}}.

Also valuable for {{OEIS2C|id=A027641}} / {{OEIS2C|id=A027642}} (see [[#Connection with Worpitzky numbers|Connection with Worpitzky numbers]]).

===Connection with Pascal's triangle===
There are formulas connecting Pascal's triangle to Bernoulli numbers{{efn|this formula was discovered (or perhaps rediscovered) by Giorgio Pietrocola. His demonstration is available in Italian language {{harv|Pietrocola|2008}}.}}
:<math> B^{+}_n=\frac{|A_n|}{(n+1)!}~~~</math>
where <math>|A_n|</math> is the determinant of a n-by-n [[Hessenberg matrix]] part of [[Pascal's triangle]] whose elements are: <math>
a_{i, k} = \begin{cases} 
0 & \text{if } k>1+i \\
{i+1 \choose k-1} & \text{otherwise}
\end{cases}
</math>

Example:

:<math> B^{+}_6 =\frac{\det\begin{pmatrix}
1& 2& 0& 0& 0& 0\\
1& 3& 3& 0& 0& 0\\
1& 4& 6& 4& 0& 0\\
1& 5& 10& 10& 5& 0\\
1& 6& 15& 20& 15& 6\\
1& 7& 21& 35& 35& 21
\end{pmatrix}}{7!}=\frac{120}{5040}=\frac 1 {42}
</math>

=== Connection with Eulerian numbers ===
There are formulas connecting [[Eulerian number]]s {{math|<big><big>⟨</big></big>{{su|p=''n''|b=''m''|a=c}}<big><big>⟩</big></big>}} to Bernoulli numbers:

:<math>\begin{align}
\sum_{m=0}^n (-1)^m \left \langle {n\atop m} \right \rangle &= 2^{n+1} (2^{n+1}-1) \frac{B_{n+1}}{n+1}, \\
\sum_{m=0}^n (-1)^m \left \langle {n\atop m} \right \rangle \binom{n}{m}^{-1} &= (n+1) B_n.
\end{align}</math>

Both formulae are valid for {{math|''n'' ≥ 0}} if {{math|''B''<sub>1</sub>}} is set to {{sfrac|1|2}}. If {{math|''B''<sub>1</sub>}} is set to −{{sfrac|1|2}} they are valid only for {{math|''n'' ≥ 1}} and {{math|''n'' ≥ 2}} respectively.

==A binary tree representation==
The Stirling polynomials {{math|''σ''<sub>''n''</sub>(''x'')}} are related to the Bernoulli numbers by {{math|''B''<sub>''n''</sub> {{=}} ''n''!''σ''<sub>''n''</sub>(1)}}. S. C. Woon described an algorithm to compute {{math|''σ''<sub>''n''</sub>(1)}} as a binary tree:{{r|Woon1997}}

:[[File:SCWoonTree.png]]

Woon's recursive algorithm (for {{math|''n'' ≥ 1}}) starts by assigning to the root node {{math|''N'' {{=}} [1,2]}}. Given a node {{math|''N'' {{=}} [''a''<sub>1</sub>, ''a''<sub>2</sub>, ..., ''a''<sub>''k''</sub>]}} of the tree, the left child of the node is {{math|''L''(''N'') {{=}} [−''a''<sub>1</sub>, ''a''<sub>2</sub> + 1, ''a''<sub>3</sub>, ..., ''a''<sub>''k''</sub>]}} and the right child {{math|''R''(''N'') {{=}} [''a''<sub>1</sub>, 2, ''a''<sub>2</sub>, ..., ''a''<sub>''k''</sub>]}}. A node {{math|''N'' {{=}} [''a''<sub>1</sub>, ''a''<sub>2</sub>, ..., ''a''<sub>''k''</sub>]}} is written as {{math|±[''a''<sub>2</sub>, ..., ''a''<sub>''k''</sub>]}} in the initial part of the tree represented above with ± denoting the sign of {{math|''a''<sub>1</sub>}}.

Given a node {{mvar|N}} the factorial of {{mvar|N}} is defined as

:<math> N! = a_1 \prod_{k=2}^{\operatorname{length}(N)} a_k!. </math>

Restricted to the nodes {{mvar|N}} of a fixed tree-level {{mvar|n}} the sum of {{math|{{sfrac|1|''N''!}}}} is {{math|''σ''<sub>''n''</sub>(1)}}, thus

:<math> B_n = \sum_\stackrel{N \text{ node of}}{\text{ tree-level } n} \frac{n!}{N!}. </math>

For example:
:{{math|1=''B''<sub>1</sub> = 1!({{sfrac|1|2!}})}}
:{{math|1=''B''<sub>2</sub> = 2!(−{{sfrac|1|3!}} + {{sfrac|1|2!2!}})}}
:{{math|1=''B''<sub>3</sub> = 3!({{sfrac|1|4!}} − {{sfrac|1|2!3!}} − {{sfrac|1|3!2!}} + {{sfrac|1|2!2!2!}})}}

==Integral representation and continuation==

The [[integral]]
: <math> b(s) = 2e^{s i \pi/2}\int_0^\infty \frac{st^s}{1-e^{2\pi t}} \frac{dt}{t} = \frac{s!}{2^{s-1}}\frac{\zeta(s)}{{   }\pi^s{  }}(-i)^s= \frac{2s!\zeta(s)}{(2\pi i)^s}</math>
has as special values {{math|''b''(2''n'') {{=}} ''B''<sub>2''n''</sub>}} for {{math|''n'' > 0}}.

For example, {{math|1=''b''(3) = {{sfrac|3|2}}''ζ''(3)''&pi;''<sup>−3</sup>''i''}} and {{math|1=''b''(5) = −{{sfrac|15|2}}''ζ''(5)''&pi;''<sup>−5</sup>''i''}}. Here, {{mvar|ζ}} is the [[Riemann zeta function]], and {{mvar|i}} is the [[imaginary unit]]. Leonhard Euler (''Opera Omnia'', Ser. 1, Vol. 10, p.&nbsp;351) considered these numbers and calculated

: <math> \begin{align}
  p &=  \frac{3}{2\pi^3}\left(1+\frac{1}{2^3}+\frac{1}{3^3}+\cdots \right) = 0.0581522\ldots \\
  q &= \frac{15}{2\pi^5}\left(1+\frac{1}{2^5}+\frac{1}{3^5}+\cdots \right) = 0.0254132\ldots
\end{align}</math>

Another similar [[integral]] representation is
: <math> b(s) = -\frac{e^{s i \pi/2}}{2^{s}-1}\int_0^\infty \frac{st^{s}}{\sinh\pi t} \frac{dt}{t}= \frac{2e^{s i \pi/2}}{2^{s}-1}\int_0^\infty \frac{e^{\pi t}st^s}{1-e^{2\pi t}} \frac{dt}{t}. </math>

==The relation to the Euler numbers and {{pi}}==

The [[Euler number]]s are a sequence of integers intimately connected with the Bernoulli numbers. Comparing the
asymptotic expansions of the Bernoulli and the Euler numbers shows that the Euler numbers {{math|''E''<sub>2''n''</sub>}} are in magnitude approximately {{math|{{sfrac|2|π}}(4<sup>2''n''</sup> − 2<sup>2''n''</sup>)}} times larger than the Bernoulli numbers {{math|''B''<sub>2''n''</sub>}}. In consequence:

: <math> \pi \sim 2 (2^{2n} - 4^{2n}) \frac{B_{2n}}{E_{2n}}. </math>

This asymptotic equation reveals that {{pi}} lies in the common root of both the Bernoulli and the Euler numbers. In fact {{pi}} could be computed from these rational approximations.

Bernoulli numbers can be expressed through the Euler numbers and vice versa. Since, for odd {{mvar|n}}, {{math|''B''<sub>''n''</sub> {{=}} ''E''<sub>''n''</sub> {{=}} 0}} (with the exception {{math|''B''<sub>1</sub>}}), it suffices to consider the case when {{mvar|n}} is even.

:<math>\begin{align}
 B_n &= \sum_{k=0}^{n-1}\binom{n-1}{k} \frac{n}{4^n-2^n}E_k & n&=2, 4, 6, \ldots \\[6pt]
 E_n &= \sum_{k=1}^n \binom{n}{k-1} \frac{2^k-4^k}{k} B_k & n&=2,4,6,\ldots
\end{align}</math>

These conversion formulas express a connection between the Bernoulli and the Euler numbers. But more important, there is a deep arithmetic root common to both kinds of numbers, which can be expressed through a more fundamental sequence of numbers, also closely tied to {{pi}}. These numbers are defined for {{math|''n'' ≥ 1}} as<ref>{{citation
 | last = Stanley | first = Richard P. | author-link = Richard P. Stanley
 | arxiv = 0912.4240
 | contribution = A survey of alternating permutations
 | doi = 10.1090/conm/531/10466
 | mr = 2757798
 | pages = 165–196
 | publisher = American Mathematical Society | location = Providence, RI
 | series = Contemporary Mathematics
 | title = Combinatorics and graphs
 | volume = 531
 | year = 2010| isbn = 978-0-8218-4865-4 | s2cid = 14619581 }}</ref>{{r|Elkies2003}}

:<math> S_n  = 2 \left(\frac{2}{\pi}\right)^n \sum_{k = 0}^\infty \frac{ (-1)^{kn} }{(2k+1)^n} = 2 \left(\frac{2}{\pi}\right)^n \lim_{K\to \infty} \sum_{k = -K}^K (4k+1)^{-n}. </math>

The magic of these numbers lies in the fact that they turn out to be rational numbers.  This was first proved by [[Leonhard Euler]] in a landmark paper ''De summis serierum reciprocarum'' (On the sums of series of reciprocals) and has fascinated mathematicians ever since.{{r|Euler1735}} The first few of these numbers are

: <math> S_n = 1,1,\frac{1}{2},\frac{1}{3},\frac{5}{24}, \frac{2}{15},\frac{61}{720},\frac{17}{315},\frac{277}{8064},\frac{62}{2835},\ldots  </math> ({{OEIS2C|id=A099612}} / {{OEIS2C|id=A099617}})

These are the coefficients in the expansion of {{math|sec ''x'' + tan ''x''}}.

The Bernoulli numbers and Euler numbers can be understood as ''special views'' of these numbers, selected from the sequence {{math|''S''<sub>''n''</sub>}} and scaled for use in special applications.

: <math>\begin{align}
  B_{n} &= (-1)^{\left\lfloor \frac{n}{2}\right\rfloor} [ n \text{ even}] \frac{n! }{2^n - 4^n}\, S_{n}\ , & n&= 2, 3, \ldots \\
  E_n &= (-1)^{\left\lfloor \frac{n}{2}\right\rfloor} [ n \text{ even}] n! \, S_{n+1}  & n &= 0, 1, \ldots
\end{align}</math>

The expression [{{math|''n''}} even] has the value 1 if {{math|''n''}} is even and 0 otherwise ([[Iverson bracket]]).

These identities show that the quotient of Bernoulli and Euler numbers at the beginning of this section is just the special case of {{math|''R''<sub>''n''</sub> {{=}} {{sfrac|2''S''<sub>''n''</sub>|''S''<sub>''n'' + 1</sub>}}}} when {{mvar|n}} is even. The {{math|''R''<sub>''n''</sub>}} are rational approximations to {{pi}} and two successive terms always enclose the true value of {{pi}}. Beginning with {{math|''n'' {{=}} 1}} the sequence starts ({{OEIS2C|id=A132049}} / {{OEIS2C|id=A132050}}):

: <math> 2, 4, 3, \frac{16}{5}, \frac{25}{8}, \frac{192}{61}, \frac{427}{136}, \frac{4352}{1385}, \frac{12465}{3968}, \frac{158720}{50521},\ldots \quad \longrightarrow \pi. </math>

These rational numbers also appear in the last paragraph of Euler's paper cited above.

Consider the Akiyama–Tanigawa transform for the sequence {{OEIS2C|id=A046978}} ({{math|''n'' + 2}}) / {{OEIS2C|id=A016116}} ({{math|''n'' + 1}}):

:{| class="wikitable" style="text-align:right;"
! 0 
|1||{{sfrac|1|2}}||0||−{{sfrac|1|4}}||−{{sfrac|1|4}}||−{{sfrac|1|8}}||0
|-
! 1 
| {{sfrac|1|2}}|| 1|| {{sfrac|3|4}}|| 0|| −{{sfrac|5|8}}|| −{{sfrac|3|4}}||
|-
! 2 
| −{{sfrac|1|2}}|| {{sfrac|1|2}}|| {{sfrac|9|4}}|| {{sfrac|5|2}}|| {{sfrac|5|8}}|| ||
|-
! 3 
| −1|| −{{sfrac|7|2}}|| −{{sfrac|3|4}}|| {{sfrac|15|2}}|| || ||
|-
! 4 
| {{sfrac|5|2}}|| −{{sfrac|11|2}}|| −{{sfrac|99|4}}|| || || ||
|-
! 5 
| 8|| {{sfrac|77|2}}|| || || || ||
|-
! 6 
| −{{sfrac|61|2}}|| || || || || ||
|}

From the second, the numerators of the first column are the denominators of Euler's formula. The first column is −{{sfrac|1|2}} × {{OEIS2C|id=A163982}}.

==An algorithmic view: the Seidel triangle==

The sequence ''S''<sub>''n''</sub> has another unexpected yet important property: The denominators of ''S''<sub>''n''+1</sub> divide the factorial {{math|''n''!}}. In other words: the numbers {{math|1=''T''<sub>''n''</sub>&nbsp;=&nbsp;''S''<sub>''n'' + 1</sub> ''n''!}}, sometimes called [[Alternating permutations|Euler zigzag numbers]], are integers.

: <math> T_n = 1,\,1,\,1,\,2,\,5,\,16,\,61,\,272,\,1385,\,7936,\,50521,\,353792,\ldots \quad n=0, 1, 2, 3, \ldots </math> ({{OEIS2C|id=A000111}}). See ({{OEIS2C|id=A253671}}).

Their [[exponential generating function]] is the sum of the [[trigonometric functions#Reciprocal functions|secant]] and [[tangent (trigonometry)|tangent]] functions.

: <math> \sum_{n=0}^\infty T_n \frac{x^n}{n!} = \tan \left(\frac\pi4 + \frac x2\right) = \sec x + \tan x</math>.

Thus the above representations of the Bernoulli and Euler numbers can be rewritten in terms of this sequence as

:<math>\begin{align}
 B_n &= (-1)^{\left\lfloor \frac{n}{2}\right\rfloor} [n\text{ even}] \frac{n }{2^n-4^n}\, T_{n-1}\  & n &\geq 2 \\
 E_n &= (-1)^{\left\lfloor \frac{n}{2}\right\rfloor} [n\text{ even}] T_{n} & n &\geq 0
\end{align}</math>

These identities make it easy to compute the Bernoulli and Euler numbers: the Euler numbers {{math|''E''<sub>2''n''</sub>}} are given immediately by {{math|''T''<sub>2''n''</sub>}} and the Bernoulli numbers {{math|''B''<sub>2''n''</sub>}} are fractions obtained from {{math|''T''<sub>2''n'' - 1</sub>}} by some easy shifting, avoiding rational arithmetic.

What remains is to find a convenient way to compute the numbers {{math|''T''<sub>''n''</sub>}}. However, already in 1877 [[Philipp Ludwig von Seidel]] published an ingenious algorithm, which makes it simple to calculate {{math|''T''<sub>''n''</sub>}}.{{r|Seidel1877}}

{{image frame|align=none|caption=Seidel's algorithm for {{math|''T''<sub>''n''</sub>}}
|content=<math>
\begin{array}{crrrcc}
 { } & { } & {\color{red}1} & { } & { } & { } \\
 { } & {\rightarrow} & {\color{blue}1} & {\color{red}1} & { } \\
 { } & {\color{red}2} & {\color{blue}2} & {\color{blue}1} & {\leftarrow} \\
 {\rightarrow} & {\color{blue}2} & {\color{blue}4} & {\color{blue}5} & {\color{red}5} \\
 {\color{red}16} & {\color{blue}16} & {\color{blue}14} & {\color{blue}10} & {\color{blue}5} & {\leftarrow} 
\end{array}
</math>}}
#Start by putting 1 in row 0 and let {{math|''k''}} denote the number of the row currently being filled
#If {{math|''k''}} is odd, then put the number on the left end of the row {{math|''k'' − 1}} in the first position of the row {{math|''k''}}, and fill the row from the left to the right, with every entry being the sum of the number to the left and the number to the upper
#At the end of the row duplicate the last number.
#If {{math|''k''}} is even, proceed similar in the other direction.

Seidel's algorithm is in fact much more general (see the exposition of Dominique Dumont {{r|Dumont1981}}) and was rediscovered several times thereafter.

Similar to Seidel's approach D. E. Knuth and T. J. Buckholtz gave a recurrence equation for the numbers {{math|''T''<sub>2''n''</sub>}} and recommended this method for computing {{math|''B''<sub>2''n''</sub>}} and {{math|''E''<sub>2''n''</sub>}} 'on electronic computers using only simple operations on integers'.{{r|KnuthBuckholtz1967}}

V. I. Arnold{{r|Arnold1991}} rediscovered Seidel's algorithm and later Millar, Sloane and Young popularized Seidel's algorithm under the name [[boustrophedon transform]].

Triangular form:

:{| style="text-align:right"
| || || || || || || 1|| || || || || || 
|-
| || || || || || 1|| || 1|| || || || || 
|-
| || || || || 2|| || 2|| || 1|| || || || 
|-
| || || || 2|| || 4|| || 5|| || 5|| || || 
|-
| || || 16|| || 16|| || 14|| || 10|| || 5|| || 
|-
| || 16|| || 32|| || 46|| || 56|| || 61|| || 61|| 
|-
|272|| ||272|| ||256|| ||224|| ||178|| ||122|| || 61
|}

Only {{OEIS2C|id=A000657}}, with one 1, and {{OEIS2C|id=A214267}}, with two 1s, are in the OEIS.

Distribution with a supplementary 1 and one 0 in the following rows:

:{| style="text-align:right"
| || || || || || || 1|| || || || || ||   
|-
| || || || || || 0|| || 1|| || || || || 
|-
| || || || || −1|| || −1|| ||  0|| || || || 
|-
| || || || 0|| || −1|| || −2|| || −2|| || || 
|-
| || ||  5|| ||  5|| ||  4|| ||  2|| ||  0|| || 
|-
| || 0|| || 5|| || 10|| || 14|| || 16|| || 16|| 
|-
|−61|| ||−61|| ||−56|| ||−46|| ||−32|| ||−16|| || 0
|}

This is {{OEIS2C|id=A239005}}, a signed version of {{OEIS2C|id=A008280}}. The main andiagonal is {{OEIS2C|id=A122045}}. The main diagonal is {{OEIS2C|id=A155585}}. The central column is {{OEIS2C|id=A099023}}. Row sums: 1, 1, −2, −5, 16, 61.... See {{OEIS2C|id=A163747}}. See the array beginning with 1, 1, 0, −2, 0, 16, 0 below.

The Akiyama–Tanigawa algorithm applied to {{OEIS2C|id=A046978}} ({{math|''n'' + 1}}) / {{OEIS2C|id=A016116}}({{math|''n''}}) yields:

:{| style="text-align:right"
| 1|| 1|| {{sfrac|1|2}}|| 0|| −{{sfrac|1|4}}|| −{{sfrac|1|4}}|| −{{sfrac|1|8}}
|-
| 0|| 1|| {{sfrac|3|2}}|| 1|| 0|| −{{sfrac|3|4}}
|-
| −1|| −1|| {{sfrac|3|2}}|| 4|| {{sfrac|15|4}}
|-
| 0|| −5|| −{{sfrac|15|2}}|| 1
|-
| 5|| 5|| −{{sfrac|51|2}}
|-
| 0|| 61
|-
| −61
|}

'''1.''' The first column is {{OEIS2C|id=A122045}}. Its binomial transform leads to:

:{| style="text-align:right"
|-
| 1|| 1|| 0|| −2|| 0|| 16|| 0
|-
|0||−1||−2||2||16||−16
|-
|−1||−1||4||14||−32
|-
|0||5||10||−46
|-
|5||5||−56
|-
|0||−61
|-
|−61
|}

The first row of this array is {{OEIS2C|id=A155585}}. The absolute values of the increasing antidiagonals are {{OEIS2C|id=A008280}}. The sum of the antidiagonals is {{nowrap|−{{OEIS2C|id=A163747}} ({{math|''n'' + 1}}).}}

'''2.''' The second column is {{nowrap|1 1 −1 −5 5 61 −61 −1385 1385...}}. Its binomial transform yields:

:{| style="text-align:right"
|-
| 1|| 2|| 2|| −4|| −16|| 32|| 272
|-
|1||0||−6||−12||48||240
|-
|−1||−6||−6||60||192
|-
|−5||0||66||32
|-
|5||66||66
|-
|61||0
|-
|−61
|}

The first row of this array is {{nowrap|1 2 2 −4 −16 32 272 544 −7936 15872 353792 −707584...}}. The absolute values of the second bisection are the double of the absolute values of the first bisection.

Consider the Akiyama-Tanigawa algorithm applied to {{OEIS2C|id=A046978}} ({{math|''n''}}) / ({{OEIS2C|id=A158780}} ({{math|''n'' + 1}}) =&nbsp;abs({{OEIS2C|id=A117575}} ({{mvar|n}})) + 1 = {{nowrap|1, 2, 2, {{sfrac|3|2}}, 1, {{sfrac|3|4}}, {{sfrac|3|4}}, {{sfrac|7|8}}, 1, {{sfrac|17|16}}, {{sfrac|17|16}}, {{sfrac|33|32}}...}}.

:{| style="text-align:right"
|1||2||2||{{sfrac|3|2}}||1||{{sfrac|3|4}}||{{sfrac|3|4}}
|-
|−1||0||{{sfrac|3|2}}||2||{{sfrac|5|4}}||0
|-
|−1||−3||−{{sfrac|3|2}}||3||{{sfrac|25|4}}
|-
|2||−3||−{{sfrac|27|2}}||−13
|-
|5||21||−{{sfrac|3|2}}
|-
|−16||45
|-
|−61
|}

The first column whose the absolute values are {{OEIS2C|id=A000111}} could be the numerator of a trigonometric function.

{{OEIS2C|id=A163747}} is an autosequence of the first kind (the main diagonal is {{OEIS2C|id=A000004}}). The corresponding array is:

:{| style="text-align:right"
|0||−1||−1||2||5||−16||−61
|-
|−1||0||3||3||−21||−45
|-
|1||3||0||−24||−24
|-
|2||−3||−24||0
|-
|−5||−21||24
|-
|−16||45
|-
|−61
|}

The first two upper diagonals are {{nowrap|−1 3 −24 402...}} = {{math|(−1)<sup>''n'' + 1</sup>}}&nbsp;×&nbsp;{{OEIS2C|id=A002832}}. The sum of the antidiagonals is {{nowrap|0 −2 0 10...}} = 2&nbsp;×&nbsp;{{OEIS2C|id=A122045}}(''n''&nbsp;+&nbsp;1).

−{{OEIS2C|id=A163982}} is an autosequence of the second kind, like for instance {{OEIS2C|id=A164555}} / {{OEIS2C|id=A027642}}. Hence the array:

:{| style="text-align:right"
|-
|2||1||−1||−2||5||16||−61
|-
|−1||−2||−1||7||11||−77
|-
|−1||1||8||4||−88
|-
|2||7||−4||−92
|-
|5||−11||−88
|-
|−16||−77
|-
|−61
|}

The main diagonal, here {{nowrap|2 −2 8 −92...}}, is the double of the first upper one, here {{OEIS2C|id=A099023}}. The sum of the antidiagonals is {{nowrap|2 0 −4 0...}} = 2&nbsp;×&nbsp;{{OEIS2C|id=A155585}}({{math|''n'' + }}1). {{OEIS2C|id=A163747}}&nbsp;−&nbsp;{{OEIS2C|id=A163982}} =&nbsp;2&nbsp;×&nbsp;{{OEIS2C|id=A122045}}.

==A combinatorial view: alternating permutations==
{{main|Alternating permutations}}

Around 1880, three years after the publication of Seidel's algorithm, [[Désiré André]] proved a now classic result of combinatorial analysis.{{r|André1879|André1881}} Looking at the first terms of the Taylor expansion of the [[trigonometric functions]]
{{math|tan ''x''}} and {{math|sec ''x''}} André made a startling discovery.

:<math>\begin{align}
 \tan x &= x + \frac{2x^3}{3!} + \frac{16x^5}{5!} + \frac{272x^7}{7!} + \frac{7936x^9}{9!} + \cdots\\[6pt]
 \sec x &= 1 + \frac{x^2}{2!} + \frac{5x^4}{4!} + \frac{61x^6}{6!} + \frac{1385x^8}{8!} + \frac{50521x^{10}}{10!} + \cdots
\end{align}</math>

The coefficients are the [[Euler number]]s of odd and even index, respectively. In consequence the ordinary expansion of {{math|tan ''x'' + sec ''x''}} has as coefficients the rational numbers {{math|''S''<sub>''n''</sub>}}.

: <math> \tan x + \sec x = 1 + x + \tfrac{1}{2}x^2 + \tfrac{1}{3}x^3 + \tfrac{5}{24}x^4 + \tfrac{2}{15}x^5 + \tfrac{61}{720}x^6 + \cdots </math>

André then succeeded by means of a recurrence argument to show that the [[alternating permutation]]s of odd size are enumerated by the Euler numbers of odd index (also called tangent numbers) and the alternating permutations of even size by the Euler numbers of even index (also called secant numbers).

==Related sequences==
The arithmetic mean of the first and the second Bernoulli numbers are the associate Bernoulli numbers: 
{{math|1=''B''<sub>0</sub> = 1}}, {{math|1=''B''<sub>1</sub> = 0}}, {{math|1=''B''<sub>2</sub> = {{sfrac|1|6}}}}, {{math|1=''B''<sub>3</sub> = 0}}, {{math|1=''B''<sub>4</sub> = −{{sfrac|1|30}}}}, {{OEIS2C|id=A176327}} / {{OEIS2C|id=A027642}}. Via the second row of its inverse Akiyama–Tanigawa transform {{OEIS2C|id=A177427}}, they lead to Balmer series {{OEIS2C|id=A061037}} / {{OEIS2C|id=A061038}}.

The Akiyama–Tanigawa algorithm applied to {{OEIS2C|id=A060819}} ({{math|''n'' + 4}}) / {{OEIS2C|id=A145979}} ({{mvar|n}}) leads to the Bernoulli numbers {{OEIS2C|id=A027641}} / {{OEIS2C|id=A027642}}, {{OEIS2C|id=A164555}} / {{OEIS2C|id=A027642}}, or {{OEIS2C|id=A176327}} {{OEIS2C|id=A176289}} without {{math|''B''<sub>1</sub>}}, named intrinsic Bernoulli numbers {{math|''B''<sub>''i''</sub>(''n'')}}.

:{| style="text-align:center; padding-left; padding-right: 2em;"
|-
|1||{{sfrac|5|6}}||{{sfrac|3|4}}||{{sfrac|7|10}}||{{sfrac|2|3}}
|-
|{{sfrac|1|6}}||{{sfrac|1|6}}||{{sfrac|3|20}}||{{sfrac|2|15}}||{{sfrac|5|42}}
|-
|0||{{sfrac|1|30}}||{{sfrac|1|20}}||{{sfrac|2|35}}||{{sfrac|5|84}}
|-
|−{{sfrac|1|30}}||−{{sfrac|1|30}}||−{{sfrac|3|140}}||−{{sfrac|1|105}}||0
|-
|0||−{{sfrac|1|42}}||−{{sfrac|1|28}}||−{{sfrac|4|105}}||−{{sfrac|1|28}}
|}

Hence another link between the intrinsic Bernoulli numbers and the Balmer series via {{OEIS2C|id=A145979}} ({{math|''n''}}).

{{OEIS2C|id=A145979}} ({{math|''n'' − 2}}) = 0, 2, 1, 6,... is a permutation of the non-negative numbers.

The terms of the first row are f(n) = {{math|{{sfrac|1|2}} + {{sfrac|1|''n'' + 2}}}}. 2, f(n) is an autosequence of the second kind. 3/2, f(n) leads by its inverse binomial transform to 3/2 −1/2 1/3 −1/4 1/5 ... = 1/2 + log 2.

Consider g(n) = 1/2 – 1 / (n+2) = 0, 1/6, 1/4, 3/10, 1/3. The Akiyama-Tanagiwa transforms gives:

:{| style="text-align:center; padding-left; padding-right:2em;"
|-
|0||{{sfrac|1|6}}||{{sfrac|1|4}}||{{sfrac|3|10}}||{{sfrac|1|3}}||{{sfrac|5|14}}||...
|-
|−{{sfrac|1|6}}||−{{sfrac|1|6}}||−{{sfrac|3|20}}||−{{sfrac|2|15}}||−{{sfrac|5|42}}||−{{sfrac|3|28}}||...
|-
|0||−{{sfrac|1|30}}||−{{sfrac|1|20}}||−{{sfrac|2|35}}||−{{sfrac|5|84}}||−{{sfrac|5|84}}||...
|-
|{{sfrac|1|30}}||{{sfrac|1|30}}||{{sfrac|3|140}}||{{sfrac|1|105}}||0||−{{sfrac|1|140}}||...
|}

0, g(n), is an autosequence of the second kind.

Euler {{OEIS2C|id=A198631}} ({{math|''n''}}) / {{OEIS2C|id=A006519}} ({{math|''n'' + 1}}) without the second term ({{sfrac|1|2}}) are the fractional intrinsic Euler numbers {{math|''E''<sub>''i''</sub>(''n'') {{=}} 1, 0, −{{sfrac|1|4}}, 0, {{sfrac|1|2}}, 0, −{{sfrac|17|8}}, 0, ...}} The corresponding Akiyama transform is:

:{| style="text-align:center; padding-left; padding-right: 2em;"
|-
|1||1||{{sfrac|7|8}}||{{sfrac|3|4}}||{{sfrac|21|32}}
|-
|0||{{sfrac|1|4}}||{{sfrac|3|8}}||{{sfrac|3|8}}||{{sfrac|5|16}}
|-
|−{{sfrac|1|4}}||−{{sfrac|1|4}}||0||{{sfrac|1|4}}||{{sfrac|25|64}}
|-
|0||−{{sfrac|1|2}}||−{{sfrac|3|4}}||−{{sfrac|9|16}}||−{{sfrac|5|32}}
|-
|{{sfrac|1|2}}||{{sfrac|1|2}}||−{{sfrac|9|16}}||−{{sfrac|13|8}}||−{{sfrac|125|64}}
|}

The first line is {{math|''Eu''(''n'')}}. {{math|''Eu''(''n'')}} preceded by a zero is an autosequence of the first kind. It is linked to the Oresme numbers. The numerators of the second line are {{OEIS2C|id=A069834}} preceded by 0. The difference table is:

:{| style="text-align:center; padding-left; padding-right: 2em;"
|-
|0||1||1||{{sfrac|7|8}}||{{sfrac|3|4}}||{{sfrac|21|32}}||{{sfrac|19|32}}
|-
|1||0||−{{sfrac|1|8}}||−{{sfrac|1|8}}||−{{sfrac|3|32}}||−{{sfrac|1|16}}||−{{sfrac|5|128}}
|-
|−1||−{{sfrac|1|8}}||0||{{sfrac|1|32}}||{{sfrac|1|32}}||{{sfrac|3|128}}||{{sfrac|1|64}}
|}

==Arithmetical properties of the Bernoulli numbers==

The Bernoulli numbers can be expressed in terms of the Riemann zeta function as {{math|''B''<sub>''n''</sub> {{=}} −''nζ''(1 − ''n'')}} for integers {{math|''n'' ≥ 0}} provided for {{math|''n'' {{=}} 0}} the expression {{math|−''nζ''(1 − ''n'')}} is understood as the limiting value and the convention {{math|''B''<sub>1</sub> {{=}} {{sfrac|1|2}}}} is used. This intimately relates them to the values of the zeta function at negative integers. As such, they could be expected to have and do have deep arithmetical properties. For example, the [[Agoh–Giuga conjecture]] postulates that {{mvar|p}} is a prime number if and only if {{math|''pB''<sub>''p'' − 1</sub>}} is congruent to −1 modulo {{mvar|p}}. Divisibility properties of the Bernoulli numbers are related to the [[ideal class group]]s of [[cyclotomic field]]s by a theorem of Kummer and its strengthening in the [[Herbrand-Ribet theorem]], and to class numbers of real quadratic fields by [[Ankeny–Artin–Chowla congruence|Ankeny–Artin–Chowla]].

=== The Kummer theorems ===
The Bernoulli numbers are related to [[Fermat's Last Theorem]] (FLT) by [[Ernst Kummer|Kummer]]'s theorem,{{r|Kummer1850}} which says:

:If the odd prime {{mvar|p}} does not divide any of the numerators of the Bernoulli numbers {{math|''B''<sub>2</sub>, ''B''<sub>4</sub>, ..., ''B''<sub>''p'' − 3</sub>}} then {{math|''x''<sup>''p''</sup> + ''y''<sup>''p''</sup> + ''z''<sup>''p''</sup> {{=}} 0}} has no solutions in nonzero integers.

Prime numbers with this property are called [[regular prime]]s. Another classical result of Kummer are the following [[Modular arithmetic#Congruence|congruences]].{{r|Kummer1851}}

{{main|Kummer's congruence}}

:Let {{mvar|p}} be an odd prime and {{mvar|b}} an even number such that {{math|''p''&nbsp;−&nbsp;1}} does not divide {{mvar|b}}. Then for any non-negative integer {{mvar|k}}
:: <math> \frac{B_{k(p-1)+b}}{k(p-1)+b} \equiv \frac{B_{b}}{b} \pmod{p}. </math>

A generalization of these congruences goes by the name of {{math|''p''}}-adic continuity.

==={{math|''p''}}-adic continuity===

If {{mvar|b}}, {{mvar|m}} and {{mvar|n}} are positive integers such that {{mvar|m}} and {{mvar|n}} are not divisible by {{math|''p'' − 1}} and {{math|''m'' ≡ ''n'' (mod ''p''<sup>''b'' − 1</sup> (''p'' − 1))}}, then

:<math>(1-p^{m-1})\frac{B_m}{m} \equiv (1-p^{n-1})\frac{B_n} n \pmod{p^b}.</math>

Since {{math|''B''<sub>''n''</sub> {{=}} −''nζ''(1 − ''n'')}}, this can also be written

:<math>\left(1-p^{-u}\right)\zeta(u) \equiv \left(1-p^{-v}\right)\zeta(v) \pmod{p^b},</math>

where {{math|''u'' {{=}} 1 − ''m''}} and {{math|''v'' {{=}} 1 − ''n''}}, so that {{mvar|u}} and {{mvar|v}} are nonpositive and not congruent to 1 modulo {{math|''p'' − 1}}. This tells us that the Riemann zeta function, with {{math|1 − ''p''<sup>−''s''</sup>}} taken out of the Euler product formula, is continuous in the [[p-adic number|{{mvar|p}}-adic number]]s on odd negative integers congruent modulo {{math|''p'' − 1}} to a particular {{math|''a'' ≢ 1 mod (''p'' − 1)}}, and so can be extended to a continuous function {{math|''ζ''<sub>''p''</sub>(''s'')}} for all {{mvar|p}}-adic integers <math>\mathbb{Z}_p,</math> the [[p-adic zeta function|{{mvar|p}}-adic zeta function]].

=== Ramanujan's congruences ===

The following relations, due to [[Ramanujan]], provide a method for calculating Bernoulli numbers that is more efficient than the one given by their original recursive definition:

:<math>\binom{m+3}{m} B_m=\begin{cases}
\frac{m+3}{3}-\sum\limits_{j=1}^\frac{m}{6}\binom{m+3}{m-6j}B_{m-6j}, & \text{if } m\equiv 0\pmod 6;\\
\frac{m+3}{3}-\sum\limits_{j=1}^\frac{m-2}{6}\binom{m+3}{m-6j}B_{m-6j}, & \text{if } m\equiv 2\pmod 6;\\
-\frac{m+3}{6}-\sum\limits_{j=1}^\frac{m-4}{6}\binom{m+3}{m-6j}B_{m-6j}, & \text{if } m\equiv 4\pmod 6.\end{cases}</math>

=== Von Staudt–Clausen theorem ===
{{main|Von Staudt–Clausen theorem}}
The von Staudt–Clausen theorem was given by [[Karl Georg Christian von Staudt]]{{r|vonStaudt1840}} and [[Thomas Clausen (mathematician)|Thomas Clausen]]{{r|Clausen1840}} independently in 1840. The theorem states that for every {{math|''n'' > 0}},
: <math> B_{2n} + \sum_{(p-1)\,\mid\,2n} \frac1p</math>
is an integer. The sum extends over all [[prime number|primes]] {{math|''p''}} for which {{math|''p'' − 1}} divides {{math|2''n''}}.

A consequence of this is that the denominator of {{math|''B''<sub>2''n''</sub>}} is given by the product of all primes {{math|''p''}} for which {{math|''p'' − 1}} divides {{math|2''n''}}. In particular, these denominators are [[square-free]] and divisible by&nbsp;6.

=== Why do the odd Bernoulli numbers vanish? ===
The sum

:<math>\varphi_k(n) = \sum_{i=0}^n i^k - \frac{n^k} 2</math>

can be evaluated for negative values of the index {{math|''n''}}. Doing so will show that it is an [[odd function]] for even values of {{math|''k''}}, which implies that the  sum has only terms of odd index. This and the formula for the Bernoulli sum imply that {{math|''B''<sub>2''k'' + 1 − ''m''</sub>}} is 0 for {{math|''m''}} even and {{math|2''k'' + 1 − ''m'' > 1}}; and that the term for {{math|''B''<sub>1</sub>}} is cancelled by the subtraction.  The von Staudt–Clausen theorem combined with Worpitzky's representation also gives a combinatorial answer to this question (valid for ''n'' > 1).

From the von Staudt–Clausen theorem it is known that for odd {{math|''n'' > 1}} the number {{math|2''B''<sub>''n''</sub>}} is an integer. This seems trivial if one knows beforehand that the integer in question is zero. However, by applying Worpitzky's representation one gets

: <math> 2B_n =\sum_{m=0}^n (-1)^m \frac{2}{m+1}m! \left\{{n+1\atop m+1} \right\} = 0\quad(n>1 \text{ is odd})</math>

as a ''sum of integers'', which is not trivial. Here a combinatorial fact comes to surface which explains the vanishing of the Bernoulli numbers at odd index. Let {{math|''S''<sub>''n'',''m''</sub>}} be the number of surjective maps from {{math|1={1, 2, ..., ''n''}}} to {{math|1={1, 2, ..., ''m''}}}, then {{math|''S''<sub>''n'',''m''</sub> {{=}} ''m''!<big><big>{</big></big>{{su|p=''n''|b=''m''|a=c}}<big><big>}</big></big>}}. The last equation can only hold if

: <math> \sum_{\text{odd }m=1}^{n-1} \frac 2 {m^2}S_{n,m}=\sum_{\text{even } m=2}^n \frac{2}{m^2} S_{n,m} \quad (n>2 \text{ is even}). </math>

This equation can be proved by induction. The first two examples of this equation are

:{{math|1=''n'' = 4: 2 + 8 = 7 + 3}},
:{{math|1=''n'' = 6: 2 + 120 + 144 = 31 + 195 + 40}}.

Thus the Bernoulli numbers vanish at odd index because some non-obvious combinatorial identities are embodied in the Bernoulli numbers.

=== A restatement of the Riemann hypothesis ===
The connection between the Bernoulli numbers and the Riemann zeta function is strong enough to provide an alternate formulation of the [[Riemann hypothesis]] (RH) which uses only the Bernoulli numbers. In fact [[Marcel Riesz]] proved that the RH is equivalent to the following assertion:{{r|Riesz1916}}

:For every {{math|''ε'' > {{sfrac|1|4}}}} there exists a constant {{math|''C''<sub>''ε''</sub> > 0}} (depending on {{math|''ε''}}) such that {{math|{{abs|''R''(''x'')}} < ''C''<sub>''ε''</sub>''x''<sup>''ε''</sup>}} as {{math|''x'' → ∞}}.

Here {{math|''R''(''x'')}} is the [[Riesz function]]

: <math> R(x) = 2 \sum_{k=1}^\infty
\frac{k^{\overline{k}} x^{k}}{(2\pi)^{2k}\left(\frac{B_{2k}}{2k}\right)}
= 2\sum_{k=1}^\infty \frac{k^{\overline{k}}x^k}{(2\pi)^{2k}\beta_{2k}}. </math>

{{math|''n''<sup>{{overline|''k''}}</sup>}} denotes the [[Pochhammer symbol#Alternate notations|rising factorial power]] in the notation of [[D. E. Knuth]]. The numbers {{math|''β''<sub>''n''</sub> {{=}} {{sfrac|''B''<sub>''n''</sub>|''n''}}}} occur frequently in the study of the zeta function and are significant  because {{math|''β''<sub>''n''</sub>}} is a {{math|''p''}}-integer for primes {{math|''p''}} where {{math|''p'' − 1}} does not divide {{math|''n''}}.  The {{math|''β''<sub>''n''</sub>}} are called ''divided Bernoulli numbers''.

==<span id="Generalized Bernoulli numbers"></span>Generalized Bernoulli numbers==
The '''generalized Bernoulli numbers''' are certain [[algebraic number]]s, defined similarly to the Bernoulli numbers, that are related to [[Special values of L-functions|special values]] of [[Dirichlet L-function|Dirichlet {{mvar|L}}-functions]] in the same way that Bernoulli numbers are related to special values of the Riemann zeta function.

Let {{mvar|χ}} be a [[Dirichlet character]] modulo {{mvar|f}}. The generalized Bernoulli numbers attached to {{mvar|χ}} are defined by

: <math>\sum_{a=1}^f \chi(a) \frac{te^{at}}{e^{ft}-1} = \sum_{k=0}^\infty B_{k,\chi}\frac{t^k}{k!}.</math>

Apart from the exceptional {{math|''B''<sub>1,1</sub> {{=}} {{sfrac|1|2}}}}, we have, for any Dirichlet character {{mvar|χ}}, that {{math|''B''<sub>''k'',''χ''</sub> {{=}} 0}} if {{math|''χ''(−1) ≠ (−1)<sup>''k''</sup>}}.

Generalizing the relation between Bernoulli numbers and values of the Riemann zeta function at non-positive integers, one has the for all integers {{math|''k'' ≥ 1}}:

: <math>L(1-k,\chi)=-\frac{B_{k,\chi}}k,</math>

where {{math|''L''(''s'',''χ'')}} is the Dirichlet {{mvar|L}}-function of {{mvar|χ}}.{{r|Neukirch1999_VII2}}

===Eisenstein–Kronecker number===
{{main|Eisenstein–Kronecker number}}
[[Eisenstein–Kronecker number]]s are an analogue of the generalized Bernoulli numbers for [[imaginary quadratic field]]s.{{r|Charollois-Sczech|BK}} They are related to critical ''L''-values of [[Hecke character]]s.{{r|BK}}

==Appendix==
=== Assorted identities ===
{{unordered list
|1 = [[Umbral calculus]] gives a compact form of Bernoulli's formula by using an abstract symbol {{math|'''B'''}}:

: <math>S_m(n) = \frac 1 {m+1} ((\mathbf{B} + n)^{m+1} - B_{m+1}) </math>

where the symbol {{math|'''B'''<sup>''k''</sup>}} that appears during binomial expansion of the parenthesized term is to be replaced by the Bernoulli number {{math|''B<sub>k</sub>''}} (and {{math|''B''<sub>1</sub> {{=}} +{{sfrac|1|2}}}}). More suggestively and mnemonically, this may be written as a definite integral:

:<math>S_m(n) = \int_0^n (\mathbf{B}+x)^m\,dx </math>

Many other Bernoulli identities can be written compactly with this symbol, e.g.

:<math> (1-2\mathbf{B})^m  = (2-2^m) B_m  </math>

|2 = Let {{math|''n''}} be non-negative and even

:<math> \zeta(n) = \frac{(-1)^{\frac{n}{2} - 1} B_n (2\pi)^n}{2(n!)}</math>

|3 = The {{math|''n''}}th [[cumulant]] of the [[uniform distribution (continuous)|uniform]] [[probability distribution]] on the interval [−1,&nbsp;0] is {{math|{{sfrac|''B''<sub>''n''</sub>|''n''}}}}.

|4 = Let {{math|''n''? {{=}} {{sfrac|1|''n''!}}}} and {{math|''n'' ≥ 1}}. Then {{math|''B''<sub>''n''</sub>}} is the following {{math|(''n'' + 1) × (''n'' + 1)}} determinant:{{r|Malenfant2011}}

: <math>
\begin{align}
B_n & = n! \begin{vmatrix}
1 & 0 & \cdots & 0 & 1 \\
2? & 1 & \cdots & 0 & 0 \\
\vdots & \vdots & & \vdots & \vdots \\
n? & (n-1)? & \cdots & 1 & 0 \\
(n+1)? & n? & \cdots & 2? & 0
\end{vmatrix} \\[8pt]
& = n! \begin{vmatrix}
1 & 0 & \cdots & 0 & 1 \\
\frac{1}{2!} & 1 & \cdots & 0 & 0 \\
\vdots & \vdots & & \vdots & \vdots \\
\frac{1}{n!} & \frac{1}{(n-1)!} & \cdots & 1 & 0 \\
\frac{1}{(n+1)!} & \frac{1}{n!} & \cdots & \frac{1}{2!} & 0
\end{vmatrix}
\end{align}
</math>

Thus the determinant is {{math|''σ''<sub>''n''</sub>(1)}}, the [[Stirling polynomial]] at {{math|''x'' {{=}} 1}}.

|5 = For even-numbered Bernoulli numbers, {{math|''B''<sub>2''p''</sub>}} is given by the {{math|(''p'' + 1) × (''p'' + 1)}} determinant::{{r|Malenfant2011}}

:<math> B_{2p} = -\frac{(2p)!}{2^{2p} - 2} \begin{vmatrix}
1 & 0 & 0 & \cdots & 0 & 1 \\
\frac{1}{3!} & 1 & 0 & \cdots & 0 & 0 \\
\frac{1}{5!} & \frac{1}{3!} & 1 & \cdots & 0 & 0 \\
\vdots & \vdots & \vdots & & \vdots& \vdots \\
\frac{1}{(2p+1)!} & \frac{1}{(2p-1)!} & \frac{1}{(2p-3)!} &\cdots & \frac{1}{3!} & 0
\end{vmatrix}</math>

|6 = Let {{math|''n'' ≥ 1}}. Then ([[Leonhard Euler]])<ref>Euler, E41, Inventio summae cuiusque seriei ex dato termino generali </ref>

: <math> \frac{1}{n} \sum_{k=1}^n \binom{n}{k}B_k B_{n-k}+B_{n-1}=-B_n </math>

|7 = Let {{math|''n'' ≥ 1}}.  Then{{r|vonEttingshausen1827}}

: <math> \sum_{k=0}^n \binom{n+1}k (n+k+1)B_{n+k}=0 </math>

|8 = Let {{math|''n'' ≥ 0}}.  Then ([[Leopold Kronecker]] 1883)

: <math> B_n = - \sum_{k=1}^{n+1} \frac{(-1)^k}{k} \binom{n+1}{k} \sum_{j=1}^k j^n </math>

|9 = Let {{math|''n'' ≥ 1}} and {{math|''m'' ≥ 1}}.  Then{{r|Carlitz1968}}

: <math> (-1)^m \sum_{r=0}^m \binom{m}{r} B_{n+r}=(-1)^n \sum_{s=0}^n \binom{n}{s} B_{m+s} </math>

|10 = Let {{math|''n'' ≥ 4}} and

: <math> H_n=\sum_{k=1}^n k^{-1} </math>

the [[harmonic number]]. Then (H. Miki 1978)

: <math> \frac{n}{2}\sum_{k=2}^{n-2}\frac{B_{n-k}}{n-k}\frac{B_k}{k} - \sum_{k=2}^{n-2} \binom{n}{k}\frac{B_{n-k}}{n-k} B_k =H_n B_n</math>

|11 = Let {{math|''n'' ≥ 4}}. [[Yuri Matiyasevich]] found (1997)

: <math> (n+2)\sum_{k=2}^{n-2}B_k B_{n-k}-2\sum_{l=2}^{n-2}\binom{n+2}{l} B_l B_{n-l}=n(n+1)B_n </math>

|12 = ''Faber–[[Rahul Pandharipande|Pandharipande]]–[[Zagier]]–Gessel identity'': for {{math|''n'' ≥ 1}},

: <math> \frac{n}{2}\left(B_{n-1}(x)+\sum_{k=1}^{n-1}\frac{B_{k}(x)}{k}
\frac{B_{n-k}(x)}{n-k}\right) -\sum_{k=0}^{n-1}\binom{n}{k}\frac{B_{n-k}}
{n-k} B_k(x) =H_{n-1}B_n(x).</math>

Choosing {{math|''x'' {{=}} 0}} or {{math|''x'' {{=}} 1}} results in the Bernoulli number identity in one or another convention.

|13 = The next formula is true for {{math|''n'' ≥ 0}} if {{math|''B''<sub>1</sub> {{=}} ''B''<sub>1</sub>(1) {{=}} {{sfrac|1|2}}}}, but only for {{math|''n'' ≥ 1}} if {{math|''B''<sub>1</sub> {{=}} ''B''<sub>1</sub>(0) {{=}} −{{sfrac|1|2}}}}.

:<math> \sum_{k=0}^n \binom{n}{k} \frac{B_k}{n-k+2} = \frac{B_{n+1}}{n+1} </math>

|14 = Let {{math|''n'' ≥ 0}}. Then

:<math> -1 + \sum_{k=0}^n \binom{n}{k} \frac{2^{n-k+1}}{n-k+1}B_k(1) = 2^n </math>

and

:<math> -1 + \sum_{k=0}^n \binom{n}{k} \frac{2^{n-k+1}}{n-k+1}B_{k}(0) = \delta_{n,0} </math>

|15 = A reciprocity relation of M.&nbsp;B.&nbsp;Gelfand:{{r|AgohDilcher2008}}

: <math> (-1)^{m+1} \sum_{j=0}^k \binom{k}{j} \frac{B_{m+1+j}}{m+1+j} + (-1)^{k+1} \sum_{j=0}^m \binom{m}{j}\frac{B_{k+1+j}}{k+1+j} = \frac{k!m!}{(k+m+1)!} </math>

}}

== See also ==
{{div col|colwidth=20em}}
* [[Bernoulli polynomial]]
* [[Bernoulli polynomials of the second kind]]
* [[Bernoulli umbra]]
* [[Bell number]]
* [[Euler number]]
* [[Genocchi number]]
* [[Kummer's congruences]]
* [[Poly-Bernoulli number]]
* [[Hurwitz zeta function]]
* [[Euler summation]]
* [[Stirling polynomial]]
* [[Sums of powers]]
{{div col end}}

== Notes ==
{{Notelist}}

== References ==
{{reflist|refs=

<ref name=Weisstein2016>{{mathworld|id=BernoulliNumber |title=Bernoulli Number|mode=cs2}}</ref>

<ref name=Selin1997_891>{{citation |editor-last=Selin |editor-first=Helaine | editor-link=Helaine Selin |date=1997 |title=Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures |isbn=0-7923-4066-3 |at=p. 819 (p. 891) |publisher=Springer |bibcode=2008ehst.book.....S}}</ref>

<ref name=SmithMikami1914_108>{{citation |last1=Smith |first1=David Eugene |last2=Mikami |first2=Yoshio |date=1914 |title=A history of Japanese mathematics |publisher=Open Court publishing company |page=108 |isbn=9780486434827 |url=https://books.google.com/books?id=pTcQsvfbSu4C}}</ref>

<ref name=Kitagawa>{{citation|last=Kitagawa|first=Tomoko L.|date=2021-07-23|title=The Origin of the Bernoulli Numbers: Mathematics in Basel and Edo in the Early Eighteenth Century|journal=The Mathematical Intelligencer|volume=44 |pages=46–56 |language=en|doi=10.1007/s00283-021-10072-y|issn=0343-6993|doi-access=free}}</ref>

<ref name=Menabrea1842_noteG>{{citation |last=Menabrea |first=L.F. |date=1842 |title=Sketch of the Analytic Engine invented by Charles Babbage, with notes upon the Memoir by the Translator Ada Augusta, Countess of Lovelace |journal=Bibliothèque Universelle de Genève |volume=82 |at=See ''Note G'' |url=http://www.fourmilab.ch/babbage/sketch.html}}</ref>

<ref name=Jacobi1834>{{citation |last=Jacobi |first=C.G.J. |author-link=Carl Gustav Jacob Jacobi |title=De usu legitimo formulae summatoriae Maclaurinianae |journal=Journal für die reine und angewandte Mathematik |volume=12 |date=1834 |pages=263–272 |url=https://zenodo.org/record/1448824 }}</ref>

<ref name="Saalschütz1893">{{citation |last=Saalschütz |first=Louis |date=1893 |title=Vorlesungen über die Bernoullischen Zahlen, ihren Zusammenhang mit den Secanten-Coefficienten und ihre wichtigeren Anwendungen |place=Berlin |publisher=Julius Springer |url=http://digital.library.cornell.edu/cgi/t/text/text-idx?c=math;idno=00450002 }}.</ref>

<ref name=BuhlerCraErnMetShokrollahi2001>{{citation |last1=Buhler |first1=J. |last2=Crandall |first2=R. |last3=Ernvall |first3=R. |last4=Metsankyla |first4=T. |last5=Shokrollahi |first5=M. |title=Irregular Primes and Cyclotomic Invariants to 12 Million |journal=Journal of Symbolic Computation |volume=31 |issue=1–2 |date=2001 |pages=89–96 |doi=10.1006/jsco.1999.1011|doi-access=free }}</ref>

<ref name=Harvey2010>{{citation |last=Harvey |first=David |date=2010 |title=A multimodular algorithm for computing Bernoulli numbers |journal=Math. Comput. |volume=79 |issue=272 |pages=2361–2370 |arxiv=0807.1347 |doi=10.1090/S0025-5718-2010-02367-1 |zbl=1215.11016 |s2cid=11329343 }}</ref>

<ref name=Kellner2002>{{citation |last=Kellner |first=Bernd |date=2002 |title=Program Calcbn – A program for calculating Bernoulli numbers |url=http://www.bernoulli.org/}}.</ref>

<ref name=Pavlyk29Apr2008>{{citation |last=Pavlyk |first=Oleksandr |date=29 April 2008 |title=Today We Broke the Bernoulli Record: From the Analytical Engine to Mathematica |website=Wolfram News |url=http://blog.wolfram.com/2008/04/29/today-we-broke-the-bernoulli-record-from-the-analytical-engine-to-mathematica/}}.</ref>

<ref name=GuoZeng2005>{{citation |last1=Guo |first1=Victor J. W. |last2=Zeng |first2=Jiang |date=30 August 2005 |title=A q-Analogue of Faulhaber's Formula for Sums of Powers |journal=The Electronic Journal of Combinatorics |volume=11 |issue=2 |doi=10.37236/1876 |bibcode=2005math......1441G |arxiv=math/0501441 |s2cid=10467873 }}</ref>

<!--<ref name=Comtet1974>{{citation |last=Comtet |first=L. |date=1974 |title=Advanced combinatorics. The art of finite and infinite expansions|edition=Revised and Enlarged |location=Dordrecht-Boston |publisher=D. Reidel Publ.}}</ref>  -->

<ref name=Rademacher1973>{{citation |last=Rademacher |first=H. |date=1973 |title=Analytic Number Theory |location=New York City |publisher=Springer-Verlag}}.</ref>

<ref name=Boole1880>{{citation |last=Boole |first=G. |date=1880 |title=A treatise of the calculus of finite differences |edition=3rd |place=London |publisher=Macmillan}}.</ref>

<ref name=Gould1972>{{citation |last=Gould |first=Henry W. |title=Explicit formulas for Bernoulli numbers |journal=Amer. Math. Monthly |volume=79 |issue=1 |date=1972 |pages=44–51 |doi=10.2307/2978125 |jstor=2978125}}</ref>

<ref name=Apostol2010_197>{{citation |last=Apostol |first=Tom M. |date=2010 |title=Introduction to Analytic Number Theory |publisher=Springer-Verlag |page=197}}</ref>

<ref name=Woon1997>{{citation |last=Woon |first=S. C. |title=A tree for generating Bernoulli numbers |jstor=2691054 |journal=Math. Mag. |volume=70 |issue=1 |date=1997 |pages=51–56 |doi=10.2307/2691054}}</ref>

<ref name=Elkies2003>{{citation |last=Elkies |first=N. D. |author-link=Noam Elkies |title=On the sums Sum_(k=-infinity...infinity) (4k+1)^(-n) |journal=Amer. Math. Monthly |volume=110 |issue=7 |date=2003 |pages=561–573 |doi=10.2307/3647742 |arxiv=math.CA/0101168 |jstor=3647742 }}</ref>

<ref name=Euler1735>{{citation |last=Euler |first=Leonhard |author-link=Leonhard Euler |title=De summis serierum reciprocarum |journal=Opera Omnia |volume=I.14, E 41 |date=1735 |pages=73–86 |arxiv=math/0506415 |bibcode=2005math......6415E }}</ref>

<ref name=Seidel1877>{{citation |last=Seidel |first=L. |title=Über eine einfache Entstehungsweise der Bernoullischen Zahlen und einiger verwandten Reihen |journal=Sitzungsber. Münch. Akad. |volume=4 |date=1877 |pages=157–187}}</ref>

<ref name=Dumont1981>{{citation |last=Dumont |first=D. |date=1981 |title=Matrices d'Euler-Seidel |journal=Séminaire Lotharingien de Combinatoire |volume=B05c |url=https://www.mat.univie.ac.at/~slc/opapers/s05dumont.html}}</ref>

<ref name=KnuthBuckholtz1967>{{citation |last1=Knuth |first1=D. E. |author-link1= Donald Knuth |last2=Buckholtz |first2=T. J. |date=1967 |title=Computation of Tangent, Euler, and Bernoulli Numbers |journal=Mathematics of Computation |volume=21 |issue=100 |pages=663–688 |publisher=American Mathematical Society |doi=10.2307/2005010 |doi-access=free |jstor=2005010 }}</ref>

<ref name=Arnold1991>{{citation |last=Arnold |first=V. I. |date=1991 |title=Bernoulli-Euler updown numbers associated with function singularities, their combinatorics and arithmetics |journal=Duke Math. J. |volume=63 |issue=2 |pages=537–555 |doi=10.1215/s0012-7094-91-06323-4}}</ref>

<ref name="André1879">{{citation |last=André |first=D. |title=Développements de sec x et tan x |journal=C. R. Acad. Sci. |volume=88 |date=1879 |pages=965–967}}</ref>

<ref name="André1881">{{citation |last=André |first=D. |title=Mémoire sur les permutations alternées |journal=Journal de Mathématiques Pures et Appliquées |volume=7 |date=1881 |pages=167–184}}</ref>

<ref name=Kummer1850>{{citation |last=Kummer |first=E. E. |author-link=Ernst Kummer |title=Allgemeiner Beweis des Fermat'schen Satzes, dass die Gleichung x<sup>λ</sup> + y<sup>λ</sup> = z<sup>λ</sup> durch ganze Zahlen unlösbar ist, für alle diejenigen Potenz-Exponenten λ, welche ungerade Primzahlen sind und in den Zählern der ersten (λ-3)/2 Bernoulli'schen Zahlen als Factoren nicht vorkommen |journal=J. Reine Angew. Math. |volume=40 |date=1850 |pages=131–138 |url=http://www.digizeitschriften.de/resolveppn/GDZPPN002146738}}</ref>

<ref name=Kummer1851>{{citation |last=Kummer |first=E. E. |author-link=Ernst Kummer |title=Über eine allgemeine Eigenschaft der rationalen Entwicklungscoefficienten einer bestimmten Gattung analytischer Functionen |journal=J. Reine Angew. Math. |volume=1851 |issue=41 |date=1851 |pages=368–372 |url=http://eudml.org/doc/147490 }}</ref>

<ref name=vonStaudt1840>{{citation |last=von Staudt |first=K. G. Ch. |title=Beweis eines Lehrsatzes, die Bernoullischen Zahlen betreffend |journal=Journal für die reine und angewandte Mathematik |volume=21 |date=1840 |pages=372–374}}</ref>

<ref name=Clausen1840>{{citation |last=Clausen |first=Thomas |title=Lehrsatz aus einer Abhandlung über die Bernoullischen Zahlen |journal=Astron. Nachr. |volume=17 |date=1840 |issue=22 |pages=351–352 |doi=10.1002/asna.18400172205}}</ref>

<ref name=Riesz1916>{{citation |last=Riesz |first=M. |title=Sur l'hypothèse de Riemann |journal=Acta Mathematica |volume=40 |date=1916 |pages=185–90 |doi=10.1007/BF02418544 |doi-access=free }}</ref>

<ref name=Neukirch1999_VII2>{{Neukirch ANT|mode=cs2}} §VII.2.</ref>

<ref name=Malenfant2011>{{cite arXiv |eprint=1103.1585 |last=Malenfant |first=Jerome |date=2011 |title=Finite, closed-form expressions for the partition function and for Euler, Bernoulli, and Stirling numbers |class=math.NT|mode=cs2}}</ref>

<ref name=vonEttingshausen1827>{{citation |last=von Ettingshausen |first=A. |date=1827 |title=Vorlesungen über die höhere Mathematik |volume=1 |location=Vienna |publisher=Carl Gerold}}</ref>

<ref name=Carlitz1968>{{citation |last=Carlitz |first=L. |title=Bernoulli Numbers |journal=[[Fibonacci Quarterly]] |volume=6 |pages=71–85 |date=1968|issue=3 |doi=10.1080/00150517.1968.12431229 }}</ref>

<ref name=AgohDilcher2008>{{citation |last1=Agoh |first1=Takashi|last2=Dilcher |first2=Karl  |title=Reciprocity Relations for Bernoulli Numbers |journal=American Mathematical Monthly |volume=115 |issue=3 |date=2008 |pages=237–244 |jstor=27642447 |doi=10.1080/00029890.2008.11920520 |s2cid=43614118 }}</ref>

<ref name=Charollois-Sczech>{{citation |last1=Charollois |first1=Pierre |last2=Sczech |first2=Robert |year=2016 |title=Elliptic Functions According to Eisenstein and Kronecker: An Update |journal=EMS Newsletter |language=en |volume=2016-9 |issue=101 |pages=8–14 |doi=10.4171/NEWS/101/4 |s2cid=54504376 |issn=1027-488X|doi-access=free }}</ref>

<ref name=BK>{{citation |last1=Bannai |first1=Kenichi |last2=Kobayashi |first2=Shinichi |year=2010 |title=Algebraic theta functions and the p-adic interpolation of Eisenstein-Kronecker numbers |url=https://projecteuclid.org/journals/duke-mathematical-journal/volume-153/issue-2/Algebraic-theta-functions-and-the-p-adic-interpolation-of-Eisenstein/10.1215/00127094-2010-024.full |journal=[[Duke Mathematical Journal]] |volume=153 |issue=2 |doi=10.1215/00127094-2010-024 |arxiv=math/0610163 |s2cid=9262012 |issn=0012-7094}}</ref>

}}

== Bibliography ==
* {{citation |last1=Abramowitz |first1=M. |last2=Stegun |first2=I. A. |contribution=§23.1: Bernoulli and Euler Polynomials and the Euler-Maclaurin Formula |title=Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables |edition=9th printing |location=New York |publisher=Dover Publications|pages=804–806 |date=1972}}.
* {{citation|last=Arfken |first=George |date=1970 |title=Mathematical methods for physicists |edition=2nd |publisher=Academic Press |isbn=978-0120598519}}
* {{citation |first=D. |last=Arlettaz |title=Die Bernoulli-Zahlen: eine Beziehung zwischen Topologie und Gruppentheorie |journal=Math. Semesterber |volume=45 |date=1998 |pages=61–75 |doi=10.1007/s005910050037|s2cid=121753654 }}.
* {{citation |first=A. |last=Ayoub |title=Euler and the Zeta Function |journal=Amer. Math. Monthly |volume=74 |date=1981 |issue=2 |pages=1067–1086 |jstor=2319041| doi=10.2307/2319041}}.
* {{citation |first1=John |last1=Conway |author-link1=John Horton Conway |first2=Richard |last2=Guy |author-link2=Richard K. Guy |title=The Book of Numbers |publisher=Springer-Verlag |date=1996}}.
* {{citation |title=Bernoulli numbers. Bibliography (1713–1990) |first1=K. |last1=Dilcher |first2=L. |last2=Skula |first3=I. Sh. |last3=Slavutskii |journal=Queen's Papers in Pure and Applied Mathematics |location=Kingston, Ontario |date=1991 |url=http://www.mscs.dal.ca/~dilcher/bernoulli.html |issue=87}}.
*{{citation |first1=D. |last1=Dumont |first2=G. |last2=Viennot |title=A combinatorial interpretation of Seidel generation of Genocchi numbers |journal=Ann. Discrete Math. |volume=6 |date=1980 |pages=77–87 |doi=10.1016/S0167-5060(08)70696-4 |series=Annals of Discrete Mathematics |isbn=978-0-444-86048-4}}.
* {{citation |last=Entringer |first=R. C. |title=A combinatorial interpretation of the Euler and Bernoulli numbers |journal=Nieuw. Arch. V. Wiskunde |volume=14 |date=1966 |pages=241–6}}.
* {{cite arXiv |first1=G. |last1=Fee |first2=S. |last2=Plouffe |date=2007 |title=An efficient algorithm for the computation of Bernoulli numbers |eprint=math/0702300|mode=cs2}}.
* {{citation |last1=Graham |first1=R. |author-link1=Ronald Graham |last2=Knuth |first2=D. E. |author-link2=Donald Knuth |last3=Patashnik| first3=O. |date=1989 |title=Concrete Mathematics |edition=2nd |publisher=Addison-Wesley |isbn=0-201-55802-5 }}
* {{citation|first1=Kenneth|last1=Ireland|first2=Michael|last2=Rosen|title=A Classical Introduction to Modern Number Theory|edition=2nd|publisher=Springer-Verlag|date=1990|isbn=0-387-97329-X}}
* {{citation |first=Charles |last=Jordan |title=Calculus of Finite Differences |publisher=Chelsea Publ. Co. |location=New York |date=1950}}.
* {{citation |first=M. |last=Kaneko |title=The Akiyama-Tanigawa algorithm for Bernoulli numbers |journal=Journal of Integer Sequences |volume=12 |pages=29 |date=2000 |url=http://www.cs.uwaterloo.ca/journals/JIS/vol3.html |bibcode=2000JIntS...3...29K}}.
* {{citation |last=Knuth |first=D. E. |author-link=Donald Knuth |date=1993 |title=Johann Faulhaber and the Sums of Powers |journal=Mathematics of Computation |volume=61 |issue=203 |pages=277–294 |arxiv=math/9207222 |doi=10.2307/2152953 |jstor=2152953 |publisher=American Mathematical Society}}
* {{citation |first=Peter |last=Luschny |url=http://www.luschny.de/math/primes/bernincl.html |title=An inclusion of the Bernoulli numbers |date=2007}}.
*{{citation |title=TheLostBernoulliNumbers |last=Luschny |first=Peter |work=OeisWiki |date=8 October 2011 |access-date=11 May 2019 |url= http://oeis.org/wiki/User:Peter_Luschny/TheLostBernoulliNumbers}}.
*{{citation |title=The Mathematics Genealogy Project |date=n.d. |location=Fargo |publisher=Department of Mathematics, North Dakota State University |access-date=11 May 2019 |url=https://www.genealogy.math.ndsu.nodak.edu/ |ref={{SfnRef|Mathematics Genealogy Project|n.d.}} |archive-url=https://web.archive.org/web/20190510171712/https://genealogy.math.ndsu.nodak.edu/ |archive-date=10 May 2019 |url-status=dead }}.
*{{citation |title=Earliest Uses of Symbols of Calculus |last=Miller |first=Jeff |work=Earliest Uses of Various Mathematical Symbols |date=23 June 2017 |access-date=11 May 2019 |url= http://jeff560.tripod.com/calculus.html}}.
*{{citation |first1=John W. |last1=Milnor |author-link1=John Milnor |first2=James D. |last2=Stasheff |contribution=Appendix B: Bernoulli Numbers |pages=281–287 |title=Characteristic Classes |series=Annals of Mathematics Studies |volume=76 |publisher=Princeton University Press and University of Tokyo Press |date=1974}}.
* {{citation |url=http://www.maecla.it/Matematica/sommapotenze/teorema_1B.htm#teorema1b |title=Esplorando un antico sentiero: teoremi sulla somma di potenze di interi successivi (Corollario 2b)|last=Pietrocola |first=Giorgio |date=October 31, 2008 |website=Maecla |access-date=April 8, 2017|language=it}}.
* {{citation |first=Ilya Sh. |last=Slavutskii |title=Staudt and arithmetical properties of Bernoulli numbers |journal=Historia Scientiarum |volume=2 |date=1995 |pages=69–74}}.
* {{citation |first=K. G. Ch. |last=von Staudt |contribution=De numeris Bernoullianis, commentationem alteram |title=Erlangen |date=1845}}.
*{{citation |first=Zhi-Wei |last=Sun |title=Some curious results on Bernoulli and Euler polynomials |date=2005–2006 |url=http://pweb.nju.edu.cn/zwsun |archive-url=https://web.archive.org/web/20011031073728/http://pweb.nju.edu.cn/zwsun/ |url-status=dead |archive-date=2001-10-31 }}.
* {{cite arXiv |first=S. C. |last=Woon |title=Generalization of a relation between the Riemann zeta function and Bernoulli numbers |date=1998 |eprint=math.NT/9812143 |mode=cs2}}.
* {{citation |first=J. |last=Worpitzky |title=Studien über die Bernoullischen und Eulerschen Zahlen |journal=Journal für die reine und angewandte Mathematik |volume=94 |date=1883 |pages=203–232 |url=http://resolver.sub.uni-goettingen.de/purl?GDZPPN002158698}}.

==External links==
* {{springerEOM |title=Bernoulli numbers|id=p/b015640}}
* ''[[:gutenberg:2586|The first 498 Bernoulli Numbers]]'' from [[Project Gutenberg]]
* [https://web.archive.org/web/20160304004018/http://web.maths.unsw.edu.au/~davidharvey/papers/bernmm/ A multimodular algorithm for computing Bernoulli numbers]
* [http://www.bernoulli.org The Bernoulli Number Page]
* [[:literateprograms:Category:Bernoulli numbers|Bernoulli number programs]] at [http://en.literateprograms.org LiteratePrograms]
* {{citation |author=P. Luschny |title= The Computation of Irregular Primes |url=http://www.luschny.de/math/primes/irregular.html}}
* {{citation |author=P. Luschny |title=The Computation And Asymptotics Of Bernoulli Numbers |url=http://oeis.org/wiki/User:Peter_Luschny/ComputationAndAsymptoticsOfBernoulliNumbers}}
* {{citation |author=Gottfried Helms |title= Bernoullinumbers in context of Pascal-(Binomial)matrix |url=http://go.helms-net.de/math/pascal/bernoulli_en.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://go.helms-net.de/math/pascal/bernoulli_en.pdf |archive-date=2022-10-09 |url-status=live}}
* {{citation |author=Gottfried Helms |title=summing of like powers in context with Pascal-/Bernoulli-matrix |url=http://go.helms-net.de/math/binomial/04_3_SummingOfLikePowers.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://go.helms-net.de/math/binomial/04_3_SummingOfLikePowers.pdf |archive-date=2022-10-09 |url-status=live}}
* {{citation |author=Gottfried Helms |title=Some special properties, sums of Bernoulli-and related numbers |url=http://go.helms-net.de/math/binomial/02_2_GeneralizedBernoulliRecursion.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://go.helms-net.de/math/binomial/02_2_GeneralizedBernoulliRecursion.pdf |archive-date=2022-10-09 |url-status=live}}

{{Calculus topics}}
{{authority control}}

[[Category:Number theory]]
[[Category:Topology]]
[[Category:Integer sequences]]
[[Category:Eponymous numbers in mathematics]]