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

Terms

a(0) =1a(1) =25a(2) =81a(3) =169a(4) =289a(5) =441a(6) =625a(7) =841a(8) =1089a(9) =1369a(10) =1681a(11) =2025a(12) =2401a(13) =2809a(14) =3249a(15) =3721a(16) =4225a(17) =4761a(18) =5329a(19) =5929a(20) =6561a(21) =7225a(22) =7921a(23) =8649a(24) =9409a(25) =10201a(26) =11025a(27) =11881a(28) =12769a(29) =13689