a(n) = n^2 + 3*n - 1.

Terms

a(0) =-1a(1) =3a(2) =9a(3) =17a(4) =27a(5) =39a(6) =53a(7) =69a(8) =87a(9) =107a(10) =129a(11) =153a(12) =179a(13) =207a(14) =237a(15) =269a(16) =303a(17) =339a(18) =377a(19) =417a(20) =459a(21) =503a(22) =549a(23) =597a(24) =647a(25) =699a(26) =753a(27) =809a(28) =867a(29) =927