A272359 Numbers n such that (2^n - 1) / gcd(n, 2^n - 1) is not squarefree.

364, 728, 1092, 1456, 1755, 1820, 2184, 2548, 2912, 3276, 3510, 3640, 4004, 4368, 4732, 5096, 5265, 5460, 5824, 6188, 6552, 6916, 7020, 7280, 7644, 8008, 8372, 8736, 8775, 9100, 9464, 9828, 10192, 10530, 10556, 10920, 11284, 11648, 12012, 12285, 12376, 12740, 13104, 13468

Offset

1,1

Comments

Multiples of A002326((q-1)/2), where q is a Wieferich prime A001220.

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Prog

(PARI) isok(n) = my(m=2^n-1); !issquarefree(m/gcd(n, m)); \\ Michel Marcus, Apr 27 2016

Crossrefs

Cf. A049094, A272361.

Sequence in context: A004534 A256087 A260837 * A351541 A023697 A038468

Adjacent sequences: A272356 A272357 A272358 * A272360 A272361 A272362

Keyword

nonn

Author

Thomas Ordowski, Apr 27 2016

Status

approved