A067660 Values of gcd(k!+1,2^k+1) not equal to 1 taking k in increasing order.

2, 11, 19, 43, 67, 131, 163, 179, 227, 347, 419, 443, 491, 523, 563, 571, 619, 683, 691, 739, 787, 947, 1019, 1051, 1091, 1123, 1187, 1291, 1451, 1499, 1571, 1579, 1667, 1723, 1747, 1867, 1907, 1931, 2003, 2131, 2203, 6043, 2347, 2371, 2531, 2579, 2659

Offset

1,1

Links

Amiram Eldar, Table of n, a(n) for n = 1..10000

Formula

If 2m+1 is prime and is in the sequence, 2m+1 = gcd(m!+1, 2^m+1).

Mathematica

Table[GCD[n!+1, 2^n+1], {n, 0, 4000}]/.(1->Nothing) (* Harvey P. Dale, Aug 03 2018 *)

Prog

(PARI) for(k=0, 3000, d=gcd(k!+1, 2^k+1); if(d<>1, print1(d, ", ")))

Crossrefs

Cf. A068481.

Sequence in context: A163997 A067931 A186267 * A235472 A217308 A105076

Adjacent sequences: A067657 A067658 A067659 * A067661 A067662 A067663

Keyword

nonn

Author

Benoit Cloitre, Feb 03 2002

Extensions

Corrected and extended by Rick L. Shepherd, May 20 2002

Offset corrected by Amiram Eldar, Jun 06 2022

Status

approved