a(n) = n*(n-1)*(n^2 + 2)/6.

Terms

a(0) =0a(1) =0a(2) =2a(3) =11a(4) =36a(5) =90a(6) =190a(7) =357a(8) =616a(9) =996a(10) =1530a(11) =2255a(12) =3212a(13) =4446a(14) =6006a(15) =7945a(16) =10320a(17) =13192a(18) =16626a(19) =20691a(20) =25460a(21) =31010a(22) =37422a(23) =44781a(24) =53176a(25) =62700a(26) =73450a(27) =85527a(28) =99036a(29) =114086