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