A068482 Numbers n such that gcd(n!+1,2^n-1)>1.

2, 3, 4, 6, 10, 12, 16, 18, 22, 23, 28, 30, 36, 39, 40, 42, 46, 51, 52, 58, 60, 63, 66, 70, 72, 78, 82, 88, 95, 96, 99, 100, 102, 106, 108, 112, 126, 130, 131, 135, 136, 138, 148, 150, 156, 162, 166, 172, 178, 180, 183, 190, 191, 192, 196, 198, 210, 215, 222, 226

Offset: 1

Author

Benoit Cloitre, Mar 10 2002

Keywords

• easy
• nonn

Comments

If n=p-1, p prime, then n is in the sequence.

Links

• G. C. Greubel, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A000225 (2^n-1), A038507 (n!+1).

Cf. A068480, A068481, A068483.

Programs

GAP

Filtered([1..230],n->Gcd(Factorial(n)+1,2^n-1)>1); # Muniru A Asiru, Oct 16 2018

Maple

select(n->gcd(factorial(n)+1,2^n-1)>1,[$1..230]); # Muniru A Asiru, Oct 16 2018

Mathematica

Select[Range[300],GCD[#!+1,2^#-1]>1&] (* Harvey P. Dale, Jan 31 2015 *)

PARI

isok(n) = gcd(n!+1,2^n-1) > 1; \\ Michel Marcus, Oct 16 2018