1,1

a(n) mod 3 = 0 if neither prime = 3.

a(n) mod 3 = 1 if one prime = 3.

a(1) mod 3 = 2 (where both primes = 3).

Table of n, a(n) for n=1..51.

a(n) = (A143850(n)-1)/4.

Sequence in context: A141437 A219645 A186708 * A097457 A321612 A259983

Adjacent sequences: A227694 A227695 A227696 * A227698 A227699 A227700

nonn

Richard R. Forberg, Sep 22 2013

approved