OEIS joke: 1,2,3,5,6,7,8,9,10,11,12,13,...
Prime or Mod[Gamma@n,n]==0. (Every n>0 except 4.)
On 2018-12-31 15:18, D J Makin via math-fun wrote:
> Well the simplest math expression to test if n is prime I’d guess is
> that n is prime if (gamma(n)^2)%n is not zero ;)
> I tested this using the mathematically simpler and smaller (but
> somewhat slower?) ((n-1)!*p!)%n where p! is the product of
> the primes less than n and with the exact equivalent to the gamma
> version ((n-1)!^2)%n.
> Not much use for huge primes without an incredibly fast and incredibly
> accurate method of evaluating the gamma function.
>
