a(n) = (8*n + 1)^2*(4*n + 1).

Terms

a(0) =1a(1) =405a(2) =2601a(3) =8125a(4) =18513a(5) =35301a(6) =60025a(7) =94221a(8) =139425a(9) =197173a(10) =269001a(11) =356445a(12) =461041a(13) =584325a(14) =727833a(15) =893101a(16) =1081665a(17) =1295061a(18) =1534825a(19) =1802493a(20) =2099601a(21) =2427685a(22) =2788281a(23) =3182925a(24) =3613153a(25) =4080501a(26) =4586505a(27) =5132701a(28) =5720625a(29) =6351813