rida-hamadani / leanhs1960

Hoffman-Singleton Theorem

The purpose of this repository is to formally prove the Hoffman-Singleton theorem.

Warning

The proof still has some sorrys. PRs are welcome!

Why?

If the question is "why formalize?", refer to this ¹. If the question is "why formalize the Hoffman-Singleton theorem?", then the reasons are:

• It is often used as an example in books related to combinatorics ^{2 3}.
• An unsolved problem is related ⁴.
• I'm interested in formalizing a proof that uses multiple areas of math.
• It is a beautiful result!

Footnotes

1. Patrick Massot, Why formalize mathematics? ↩

2. Laszlo Babai and Peter Frankl, Linear Algebra Methods in Combinatorics, ver. 2.2, pp. 26-29. ↩

3. Donald Knuth, The Art of Computer Programming, Vol. 4A, pp. 7. ↩

4. Vance Faber, Jonathan Keegan, Existence of a Moore graph of degree 57 is still open. ↩