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

A034866

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

Terms

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

External references