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

Terms

a(0) =-1a(1) =2a(2) =13a(3) =32a(4) =59a(5) =94a(6) =137a(7) =188a(8) =247a(9) =314a(10) =389a(11) =472a(12) =563a(13) =662a(14) =769a(15) =884a(16) =1007a(17) =1138a(18) =1277a(19) =1424a(20) =1579a(21) =1742a(22) =1913a(23) =2092a(24) =2279a(25) =2474a(26) =2677a(27) =2888a(28) =3107a(29) =3334