1,2

These numbers of the form (2^n+1)/3 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.

V. Raman, Table of n, a(n) for n = 1..83

Samuel S. Wagstaff, Jr. The Cunningham Project

Sequence in context: A020617 A299760 A020589 * A230227 A101635 A118941

Adjacent sequences: A216520 A216521 A216522 * A216524 A216525 A216526

nonn

V. Raman, Sep 08 2012

approved