A068483 Numbers n such that gcd(n!-1,2^n-1)>1.

11, 15, 35, 75, 83, 111, 119, 135, 155, 179, 219, 231, 243, 323, 359, 375, 455, 459, 483, 491, 515, 519, 525, 531, 551, 611, 615, 639, 651, 663, 699, 719, 723, 735, 771, 779, 783, 803, 879, 915, 923, 939, 999, 1043, 1103, 1119, 1175, 1199, 1271, 1323

Offset: 1

Author

Benoit Cloitre, Mar 10 2002

Keywords

• easy
• nonn

Links

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

Crossrefs

Cf. A000225 (2^n-1), A033312 (n!-1).

Cf. A068480, A068481, A068482.

Programs

Mathematica

Select[Range[2500], GCD[#! - 1, 2^# - 1] > 1 &] (* G. C. Greubel, Oct 15 2018 *)

PARI

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