A152219 Numbers n such that n! - 1 is divisible by a square greater than one.

9, 15, 105, 112, 609

Offset

1,1

Comments

Primes p such that p^2 divides m!-1 for some integer m<p see A152220.

a(6)=4929 [From Artur Jasinski, Nov 30 2008]

Links

Table of n, a(n) for n=1..5.

Mathematica

aa = {}; Do[If[(Sqrt[n! - 1] /. Sqrt[_] -> 1) > 1, Print[n]; AppendTo[aa, n], {n, 1, 1000}]; aa (*Artur Jasinski*)
nfdsQ[n_]:=AnyTrue[Rest[Divisors[n!-1]], IntegerQ[Sqrt[#]]&]; Select[Range[ 2, 610], nfdsQ] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, May 24 2020 *)

Crossrefs

A064237

Sequence in context: A304457 A219129 A226927 * A173037 A029712 A136353

Adjacent sequences: A152216 A152217 A152218 * A152220 A152221 A152222

Keyword

nonn

Author

Artur Jasinski, Nov 29 2008

Extensions

Definition clarified by Harvey P. Dale, May 24 2020

Status

approved