OFFSET
1,1
COMMENTS
For numbers k such that k! - 1 is divisible by a square see A152219.
a(7) > 60000, if it exists. - Amiram Eldar, Oct 23 2024
MATHEMATICA
aa = {}; Do[If[(Sqrt[n! - 1] /. Sqrt[_] -> 1) > 1, Print[n]; 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 *)
PROG
(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
CROSSREFS
KEYWORD
nonn,more,changed
AUTHOR
Artur Jasinski, Nov 29 2008
EXTENSIONS
a(6) from Artur Jasinski, Nov 30 2008
STATUS
approved