%I #10 Jan 29 2018 02:49:16
%S 0,1,1,2,3,3,3,5,5,6,6,6,7,9,9,9,10,10,10,12,12,14,14,14,14,15,15,16,
%T 18,18,18,20,20,20,20,20,21,23,23,25,25,25,25,27,27,27,27,27,28,31,31,
%U 31,33,33,33,33,33,35,35,35
%N Number of solutions to x^2 + x*y + y^2 <= n, excluding (0,0), divided by 6.
%F For n > 0, a(n) = Sum_{k=1..n} K(k,3)*floor(n/k) where K(x,y) is the Kronecker symbol. - _Benoit Cloitre_, Oct 31 2009
%o (PARI) a(n)=if(n<1,0,sum(k=1,n,kronecker(k,3)*floor(n/k))) \\ _Benoit Cloitre_, Oct 31 2009
%Y A014201/6. Cf. A014200.
%K nonn,easy
%O 0,4
%A _N. J. A. Sloane_