a(n) = v(n+1)/v(n), where v=A203430.

Terms

a(0) =2a(1) =3a(2) =30a(3) =72a(4) =1440a(5) =4536a(6) =142560a(7) =544320a(8) =23950080a(9) =106142400a(10) =6107270400a(11) =30569011200