a(n) = 6*n^2 + 12*n.

Terms

a(0) =18a(1) =48a(2) =90a(3) =144a(4) =210a(5) =288a(6) =378a(7) =480a(8) =594a(9) =720a(10) =858a(11) =1008a(12) =1170a(13) =1344a(14) =1530a(15) =1728a(16) =1938a(17) =2160a(18) =2394a(19) =2640a(20) =2898a(21) =3168a(22) =3450a(23) =3744a(24) =4050a(25) =4368a(26) =4698a(27) =5040a(28) =5394a(29) =5760