A227697 - OEIS

%I #11 Nov 26 2013 04:30:37

%S 2,4,6,7,9,12,16,18,21,22,24,27,30,36,37,39,42,46,48,51,57,60,66,67,

%T 69,72,81,87,90,102,106,108,111,120,121,123,126,132,135,141,150,156,

%U 165,171,172,174,177,186,192,207,210

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

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

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

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

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

%K nonn

%O 1,1

%A _Richard R. Forberg_, Sep 22 2013