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

Author

Thomas Ordowski, Apr 27 2016

Keywords

• nonn

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

Crossrefs

Cf. A049094, A272361.

Programs

PARI

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