a(n) = 400*n^2 + 20.

Terms

a(0) =20a(1) =420a(2) =1620a(3) =3620a(4) =6420a(5) =10020a(6) =14420a(7) =19620a(8) =25620a(9) =32420a(10) =40020a(11) =48420a(12) =57620a(13) =67620a(14) =78420a(15) =90020a(16) =102420a(17) =115620a(18) =129620a(19) =144420a(20) =160020a(21) =176420a(22) =193620a(23) =211620a(24) =230420a(25) =250020a(26) =270420a(27) =291620a(28) =313620a(29) =336420