Numerator of (n-1)*n*(n+1)/4.

Terms

a(0) =0a(1) =0a(2) =3a(3) =6a(4) =15a(5) =30a(6) =105a(7) =84a(8) =126a(9) =180a(10) =495a(11) =330a(12) =429a(13) =546a(14) =1365a(15) =840a(16) =1020a(17) =1224a(18) =2907a(19) =1710a(20) =1995a(21) =2310a(22) =5313a(23) =3036a(24) =3450a(25) =3900a(26) =8775a(27) =4914a(28) =5481a(29) =6090