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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
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
Sequence in context: A004534 A256087 A260837 * A351541 A023697 A038468
KEYWORD
nonn
AUTHOR
Thomas Ordowski, Apr 27 2016
STATUS
approved