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

Terms

a(0) =0a(1) =3a(2) =21a(3) =78a(4) =210a(5) =465a(6) =903a(7) =1596a(8) =2628a(9) =4095a(10) =6105a(11) =8778a(12) =12246a(13) =16653a(14) =22155a(15) =28920a(16) =37128a(17) =46971a(18) =58653a(19) =72390a(20) =88410a(21) =106953a(22) =128271a(23) =152628a(24) =180300a(25) =211575a(26) =246753a(27) =286146a(28) =330078a(29) =378885