A179458 Numbers k such that ((2^(2k) - 1) mod 2k) - (2^(2k-1) mod 2k) = 1.

1, 3, 5, 7, 11, 13, 15, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 85, 89, 91, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307

Offset: 1

Author

Juri-Stepan Gerasimov, Jan 07 2011

Keywords

• nonn

Comments

Apparently, the sequence contains 1, odd primes and the elements of A020136. - R. J. Mathar, Jan 09 2011

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001567.

Programs

Maple

select(n -> (2 &^ (2*n)-1 mod 2*n)-(2 &^(2*n-1) mod 2*n) = 1, [$1..1000]); # Robert Israel, Oct 25 2017

PARI

isok(n) = (((2^(2*n)-1) % (2*n)) - (2^(2*n-1) % (2*n)) == 1) \\ Michel Marcus, Jul 25 2013