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

Terms

a(0) =0a(1) =6a(2) =30a(3) =90a(4) =204a(5) =390a(6) =666a(7) =1050a(8) =1560a(9) =2214a(10) =3030a(11) =4026a(12) =5220a(13) =6630a(14) =8274a(15) =10170a(16) =12336a(17) =14790a(18) =17550a(19) =20634a(20) =24060a(21) =27846a(22) =32010a(23) =36570a(24) =41544a(25) =46950a(26) =52806a(27) =59130a(28) =65940a(29) =73254