A306097 Terms of A121707 not in A267999.

697, 1241, 1247, 1271, 1513, 2057, 2201, 2329, 2501, 2873, 3053, 3131, 3683, 3689, 3961, 4015, 4061, 4141, 4777, 4859, 4991, 5321, 5921, 5963, 6137, 6851, 6953, 7421, 7769, 7781, 7957, 8471, 8711, 8857, 9017, 9211, 9271, 9401, 9641, 9673, 10217, 10277, 10489, 10795, 11033, 11501

Offset: 1

Author

M. F. Hasler, following remarks from Tomasz Ordowski, Oct 03 2018

Keywords

• nonn

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.

2057 is the first term not in A008367, nor in A287391. - M. F. Hasler, Oct 04 2018

Examples

			The smallest element of this sequence is a(1) = 697 = 17*41.
		

Links

• M. F. Hasler, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A121707, A267999.

Programs

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}

Formula

A121707 \ A267999.