a(n) = (n-1)*(n+1)!/6.

A005990

a(n) = (n-1)*(n+1)!/6.

Terms

    a(0) =0a(1) =1a(2) =8a(3) =60a(4) =480a(5) =4200a(6) =40320a(7) =423360a(8) =4838400a(9) =59875200a(10) =798336000a(11) =11416204800a(12) =174356582400

External references