a(n) = n! - n.

Terms

a(0) =1a(1) =0a(2) =0a(3) =3a(4) =20a(5) =115a(6) =714a(7) =5033a(8) =40312a(9) =362871a(10) =3628790a(11) =39916789a(12) =479001588a(13) =6227020787a(14) =87178291186