a(n) = n!*(n-4)/2.

Terms

a(0) =0a(1) =60a(2) =720a(3) =7560a(4) =80640a(5) =907200a(6) =10886400a(7) =139708800a(8) =1916006400a(9) =28021593600a(10) =435891456000