A152220 Primes p such that p^2 divides m!-1 for some integer m < p.
11, 31, 107, 571, 971, 4931
Offset: 1
Programs
-
Mathematica
aa = {}; Do[If[(Sqrt[n! - 1] /. Sqrt[] -> 1) > 1, Print[(Sqrt[n! - 1] /. Sqrt[] -> 1)]; AppendTo[aa, (Sqrt[n! - 1] /. Sqrt[_] -> 1)]], {n, 1, 1000}]; aa q[p_] := Module[{m = 2}, While[m < p && ! Divisible[m! - 1, p^2], m++]; Divisible[m! - 1, p^2]]; Select[Prime[Range[660]], q] (* Amiram Eldar, Oct 23 2024 *) -
PARI
is(p) = if(isprime(p), my(m = 2); while(m < p && (m! - 1) % (p^2), m++); !((m! - 1) % (p^2)), 0); \\ Amiram Eldar, Oct 23 2024
Extensions
a(6) from Artur Jasinski, Nov 30 2008
Comments