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

Terms

a(0) =0a(1) =6a(2) =16a(3) =30a(4) =48a(5) =70a(6) =96a(7) =126a(8) =160a(9) =198a(10) =240a(11) =286a(12) =336a(13) =390a(14) =448a(15) =510a(16) =576a(17) =646a(18) =720a(19) =798a(20) =880a(21) =966a(22) =1056a(23) =1150a(24) =1248a(25) =1350a(26) =1456a(27) =1566a(28) =1680a(29) =1798