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

Terms

a(0) =0a(1) =1a(2) =6a(3) =30a(4) =100a(5) =255a(6) =546a(7) =1036a(8) =1800a(9) =2925a(10) =4510a(11) =6666a(12) =9516a(13) =13195a(14) =17850a(15) =23640a(16) =30736a(17) =39321a(18) =49590a(19) =61750a(20) =76020a(21) =92631a(22) =111826a(23) =133860a(24) =159000a(25) =187525a(26) =219726a(27) =255906a(28) =296380a(29) =341475