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Metamath is a simple and flexible computer-processable language that supports rigorously verifying, archiving, and presenting mathematical proofs. See the FAQ for more information. Metamath Proof Explorer - Constructs mathematics from scratch, starting from ZFC set theory axioms. Over 40,000 proofs. Theorem list Recent proofs (this mirror) Intuitionistic Logic Explorer - Derives mathematics from a

The aleph null above is the symbol for the first infinite cardinal number, discovered by Georg Cantor in 1873 (see Theorem aleph0). This is the starting page for the Metamath Proof Explorer subproject (set.mm database). See the main Metamath Home Page for an overview of Metamath and download links. If you wish to contribute your own proofs to the Metamath project, see How can I contribute to Metam