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A067660 Values of gcd(n!+1,2^n+1) not equal to 1 taking n in increasing order. 0
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

LINKS

Table of n, a(n) for n=0..46.

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

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

STATUS

approved

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Last modified April 20 01:03 EDT 2021. Contains 343117 sequences. (Running on oeis4.)