a(n) = 8 - 12*n + 5*n^2.

Terms

a(0) =1a(1) =4a(2) =17a(3) =40a(4) =73a(5) =116a(6) =169a(7) =232a(8) =305a(9) =388a(10) =481a(11) =584a(12) =697a(13) =820a(14) =953a(15) =1096a(16) =1249a(17) =1412a(18) =1585a(19) =1768a(20) =1961a(21) =2164a(22) =2377a(23) =2600a(24) =2833a(25) =3076a(26) =3329a(27) =3592a(28) =3865a(29) =4148