a(n) = Sum_{0<j<n} n^3-j^3.

Terms

a(0) =7a(1) =45a(2) =156a(3) =400a(4) =855a(5) =1617a(6) =2800a(7) =4536a(8) =6975a(9) =10285a(10) =14652a(11) =20280a(12) =27391a(13) =36225a(14) =47040a(15) =60112a(16) =75735a(17) =94221a(18) =115900a(19) =141120a(20) =170247a(21) =203665a(22) =241776a(23) =285000a(24) =333775a(25) =388557a(26) =449820a(27) =518056a(28) =593775a(29) =677505