A227697 Numbers of the form ((p^2 + q^2)/2 - 1)/4, where p and q are odd primes.

2, 4, 6, 7, 9, 12, 16, 18, 21, 22, 24, 27, 30, 36, 37, 39, 42, 46, 48, 51, 57, 60, 66, 67, 69, 72, 81, 87, 90, 102, 106, 108, 111, 120, 121, 123, 126, 132, 135, 141, 150, 156, 165, 171, 172, 174, 177, 186, 192, 207, 210

Offset: 1

Author

Richard R. Forberg, Sep 22 2013

Keywords

• nonn

Comments

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).

Formula

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