a(n) = T(n^3) - T(n^2), where T() are the triangular numbers (A000217).

Terms

a(0) =0a(1) =0a(2) =26a(3) =333a(4) =1944a(5) =7550a(6) =22770a(7) =57771a(8) =129248a(9) =262764a(10) =495450a(11) =879065a(12) =1483416a(13) =2400138a(14) =3746834a(15) =5671575a(16) =8357760a(17) =12029336a(18) =16956378a(19) =23461029a(20) =31923800a(21) =42790230a(22) =56577906a(23) =73883843a(24) =95392224a(25) =121882500a(26) =154237850a(27) =193454001a(28) =240648408a(29) =297069794