[Wilson's Theorem][1]


  [1]: https://en.wikipedia.org/wiki/Wilson%27s_theorem
According to Wikipedia:  

> This theorem was stated by Ibn al-Haytham (c. 1000 AD) and in the 18th
> century, by John Wilson.    Edward Waring announced the theorem in
> 1770, although neither he nor his student Wilson could prove it.
> Lagrange gave the first proof in 1771.    There is evidence that
> Leibniz was also aware of the result a century earlier, but he never
> published it.