a(n) = 8*n^2 - 3.

Terms

a(0) =5a(1) =29a(2) =69a(3) =125a(4) =197a(5) =285a(6) =389a(7) =509a(8) =645a(9) =797a(10) =965a(11) =1149a(12) =1349a(13) =1565a(14) =1797a(15) =2045a(16) =2309a(17) =2589a(18) =2885a(19) =3197a(20) =3525a(21) =3869a(22) =4229a(23) =4605a(24) =4997a(25) =5405a(26) =5829a(27) =6269a(28) =6725a(29) =7197