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

Terms

a(0) =0a(1) =0a(2) =2a(3) =30a(4) =408a(5) =5880a(6) =92880a(7) =1617840a(8) =31006080a(9) =650643840a(10) =14867193600a(11) =367913145600