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A216515
Prime numbers n such that 2^n-1 can be written in the form a^2+7*b^2.
2
3, 7, 13, 19, 31, 61, 67, 97, 103, 109, 127, 199, 229, 241, 271, 349, 457, 499, 523, 601, 607, 673, 733, 751, 823, 877, 907, 997
OFFSET
1,1
COMMENTS
These Mersenne numbers have no prime factors congruent to 3, 5 or 6 (mod 7) raised to an odd power. Also the power of 2 is not 1.
CROSSREFS
Sequence in context: A155703 A023217 A106077 * A048977 A216518 A342822
KEYWORD
nonn
AUTHOR
V. Raman, Sep 08 2012
STATUS
approved