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

Terms

a(0) =0a(1) =1a(2) =24a(3) =171a(4) =704a(5) =2125a(6) =5256a(7) =11319a(8) =22016a(9) =39609a(10) =67000a(11) =107811a(12) =166464a(13) =248261a(14) =359464a(15) =507375a(16) =700416a(17) =948209a(18) =1261656a(19) =1653019a(20) =2136000a(21) =2725821a(22) =3439304a(23) =4294951a(24) =5313024a(25) =6515625a(26) =7926776a(27) =9572499a(28) =11480896a(29) =13682229