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A068480
Numbers n such that gcd(n!-1,2^n+1)>1.
5
1, 29, 41, 53, 69, 105, 125, 141, 153, 165, 189, 233, 249, 273, 293, 321, 329, 405, 413, 429, 441, 453, 485, 581, 585, 629, 641, 653, 713, 729, 741, 761, 765, 809, 813, 849, 893, 905, 989, 993, 1005, 1013, 1041, 1049, 1089, 1121, 1125, 1133, 1169, 1205
OFFSET
1,2
LINKS
MAPLE
select(n->gcd(factorial(n)-1, 2^n+1)>1, [$1..1230]); # Muniru A Asiru, Oct 16 2018
MATHEMATICA
Select[Range[2500], GCD[#! - 1, 2^# + 1] > 1 &] (* G. C. Greubel, Oct 15 2018 *)
PROG
(PARI) isok(n) = gcd(n!-1, 2^n+1) > 1; \\ Michel Marcus, Oct 16 2018
(GAP) Filtered([1..1230], n->Gcd(Factorial(n)-1, 2^n+1)>1); # Muniru A Asiru, Oct 16 2018
CROSSREFS
Cf. A000051 (2^n+1), A033312 (n!-1).
Sequence in context: A229059 A330653 A125516 * A161616 A069454 A035789
KEYWORD
nonn
AUTHOR
Benoit Cloitre, Mar 10 2002
STATUS
approved