OFFSET
1,1
COMMENTS
Numbers n such that gcd(n, 2^n-2) > 1 and gcd(n, b^n-b) = 1 for some b > 2, b < n.
Or: Numbers n such that gcd(n, 2^n-2) > 1 and for every prime factor p of n, p-1 does not divide n-1.
LINKS
M. F. Hasler, Table of n, a(n) for n = 1..10000
EXAMPLE
The smallest element of this sequence is a(1) = 697 = 17*41.
PROG
(PARI) is(n, p)={for(i=1, #p=factor(n)[, 1], (n-1)%(p[i]-1)||return); gcd(n, lift(Mod(2, n)^n-2))>1}
CROSSREFS
KEYWORD
nonn
AUTHOR
M. F. Hasler, following remarks from Tomasz Ordowski, Oct 03 2018
STATUS
approved