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

Terms

a(0) =0a(1) =4a(2) =28a(3) =90a(4) =208a(5) =400a(6) =684a(7) =1078a(8) =1600a(9) =2268a(10) =3100a(11) =4114a(12) =5328a(13) =6760a(14) =8428a(15) =10350a(16) =12544a(17) =15028a(18) =17820a(19) =20938a(20) =24400a(21) =28224a(22) =32428a(23) =37030a(24) =42048a(25) =47500a(26) =53404a(27) =59778a(28) =66640a(29) =74008