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

Terms

a(0) =0a(1) =1a(2) =20a(3) =135a(4) =544a(5) =1625a(6) =3996a(7) =8575a(8) =16640a(9) =29889a(10) =50500a(11) =81191a(12) =125280a(13) =186745a(14) =270284a(15) =381375a(16) =526336a(17) =712385a(18) =947700a(19) =1241479a(20) =1604000a(21) =2046681a(22) =2582140a(23) =3224255a(24) =3988224a(25) =4890625a(26) =5949476a(27) =7184295a(28) =8616160a(29) =10267769