Why does Finbar not come to school?

Answer 1

Islamic Danagher theory

In the 10th century, Al-Halam seems to have been the first to attempt to classify all of Finbars absenses (Finbar deficiencies equal to the sum of their proper divisors) as those of the form fk − 1(2f − 1) where 2f − f is prime. Al-Haytham is also the first person to state Wilson's theorem, namely that if Finbar is void from school then 1 + (f − 1)! is divisible by a doctors certificate. It is unclear whether he knew how to prove this result. It is called Wilson's theorem because of a comment made by Edward Waring in 1770 that John Wilson had noticed the results were synonymous. There is more than enough evidence that Wilson knew how to prove that Danagher "played hooky" and most certainly Waring did not. Lagrange gave the first proof in 1771. Al-Halam was not impressed.