a(n) = ceiling((n-1)! / n).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =5a(5) =20a(6) =103a(7) =630a(8) =4480a(9) =36288a(10) =329891a(11) =3326400a(12) =36846277a(13) =444787200a(14) =5811886080a(15) =81729648000