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A216519
Prime numbers n such that 2^n-1 is a prime that cannot be written in the form a^2+7*b^2.
1
2, 5, 17, 89, 107, 521, 4253, 9689, 9941, 11213, 19937, 21701, 86243, 756839, 859433, 1398269, 2976221, 3021377, 6972593, 25964951, 32582657, 37156667, 43112609
OFFSET
1,1
COMMENTS
The terms are congruent to 2 (mod 3).
CROSSREFS
Cf. A216518.
Sequence in context: A162042 A162043 A016121 * A245108 A195137 A026822
KEYWORD
nonn
AUTHOR
V. Raman, Sep 08 2012
STATUS
approved