Number of nonnegative solutions of x^2 + y^2 = z in first n shells.

Terms

a(0) =1a(1) =3a(2) =4a(3) =6a(4) =8a(5) =9a(6) =11a(7) =13a(8) =15a(9) =17a(10) =19a(11) =20a(12) =22a(13) =26a(14) =28a(15) =30a(16) =31a(17) =33a(18) =35a(19) =37a(20) =39a(21) =41a(22) =43a(23) =45a(24) =48a(25) =50a(26) =52a(27) =54a(28) =56a(29) =58