a(n) = (1/3)*(n^2 + 2*n + 3)*(n+1)^2.

Terms

a(0) =1a(1) =8a(2) =33a(3) =96a(4) =225a(5) =456a(6) =833a(7) =1408a(8) =2241a(9) =3400a(10) =4961a(11) =7008a(12) =9633a(13) =12936a(14) =17025a(15) =22016a(16) =28033a(17) =35208a(18) =43681a(19) =53600a(20) =65121a(21) =78408a(22) =93633a(23) =110976a(24) =130625a(25) =152776a(26) =177633a(27) =205408a(28) =236321a(29) =270600