a(n) = n*(n-1)^3*(n^2-n-1)/2.

Terms

a(0) =0a(1) =0a(2) =1a(3) =60a(4) =594a(5) =3040a(6) =10875a(7) =30996a(8) =75460a(9) =163584a(10) =324405a(11) =599500a(12) =1046166a(13) =1740960a(14) =2783599a(15) =4301220a(16) =6453000a(17) =9435136a(18) =13486185a(19) =18892764a(20) =25995610a(21) =35196000a(22) =46962531a(23) =61838260a(24) =80448204a(25) =103507200a(26) =131828125a(27) =166330476a(28) =208049310a(29) =258144544