%I
%S 0,1,1,1,1,1,1,0,1,1,0,1,1,0,1,1,0,0,1,0,1,1,0,1,1,0,1,
%T 0,0,1,1,0,0,1,0,1,1,0,0,1,0,1,0,0,1,0,0,0,1,0,1,1,0,1,1,
%U 0,1,0,0,0,1,0,0,1,0,1,0,0,1,1,0,0,0,0,1,1,0,0,1,0,0,1,0,1,1,0,1
%N a(n) = 1 if 2*n+1 is a prime, 1 if 2*n+1 is a prime squared, or 0 otherwise.
%e a(1)=0 because 1 is neither a prime nor a prime squared;
%e a(2)=1 because 3 is a prime;
%e a(5)=1 because 9 = 3^2 is a prime squared.
%K easy,sign
%O 1,1
%A _Giovanni Teofilatto_, May 09 2005
