OFFSET
1,2
COMMENTS
Ailon and Rudnick conjecture that a(n) = 1 infinitely often.
LINKS
Antti Karttunen, Table of n, a(n) for n = 1..10000
N. Ailon and Z. Rudnick, Torsion points on curves and common divisors of a^k-1 and b^k-1, arXiv:math/0202102 [math.NT], 2002; Acta Arith. 113 (2004), no. 1, 31-38.
EXAMPLE
For n=3, 2^3-1 = 7 and 5^3-1 = 124, thus a(3) = gcd(7,124) = 1.
MAPLE
seq(igcd(2^n-1, 5^n-1), n=1..100);
MATHEMATICA
Table[GCD[2^n - 1, 5^n - 1], {n, 100}]
PROG
(Sage) [gcd(2^n-1, 5^n-1) for n in [1..100]]
(PARI) vector(100, n, gcd(2^n-1, 5^n-1))
CROSSREFS
KEYWORD
nonn
AUTHOR
Tom Edgar, Mar 16 2016
STATUS
approved