a(n)=number of Gaussian integers z=a+bi satisfying |z|<=n+1/2, a>=0, 0<=b<a.

Terms

a(0) =0a(1) =1a(2) =3a(3) =5a(4) =9a(5) =13a(6) =18a(7) =23a(8) =29a(9) =38a(10) =45a(11) =54a(12) =63a(13) =74a(14) =85a(15) =96a(16) =110a(17) =124a(18) =138a(19) =153a(20) =167a(21) =185a(22) =203a(23) =221a(24) =239a(25) =260a(26) =281a(27) =301a(28) =324a(29) =346