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A272359 Numbers n such that (2^n - 1) / gcd(n, 2^n - 1) is not squarefree. 2
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 (list; graph; refs; listen; history; text; internal format)
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 * A023697 A038468 A131348

Adjacent sequences:  A272356 A272357 A272358 * A272360 A272361 A272362

KEYWORD

nonn

AUTHOR

Thomas Ordowski, Apr 27 2016

STATUS

approved

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Last modified October 19 08:33 EDT 2021. Contains 348074 sequences. (Running on oeis4.)