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

Terms

a(0) =0a(1) =0a(2) =5a(3) =30a(4) =102a(5) =260a(6) =555a(7) =1050a(8) =1820a(9) =2952a(10) =4545a(11) =6710a(12) =9570a(13) =13260a(14) =17927a(15) =23730a(16) =30840a(17) =39440a(18) =49725a(19) =61902a(20) =76190a(21) =92820a(22) =112035a(23) =134090a(24) =159252a(25) =187800a(26) =220025a(27) =256230a(28) =296730a(29) =341852