1,1

These Mersenne numbers of the form 2^n-1 have no prime factors congruent to 3 (mod 7) or 5 (mod 7) or 6 (mod 7) to an odd power. Also the power of 2 is not 1.

Table of n, a(n) for n=1..45.

Samuel S. Wagstaff, Jr. The Cunningham Project

Sequence in context: A258117 A034017 A034021 * A310260 A310261 A038978

Adjacent sequences: A216513 A216514 A216515 * A216517 A216518 A216519

nonn

V. Raman, Sep 08 2012

approved