a(n) = n!/A000793(n).

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =6a(5) =20a(6) =120a(7) =420a(8) =2688a(9) =18144a(10) =120960a(11) =1330560a(12) =7983360a(13) =103783680a(14) =1037836800a(15) =12454041600a(16) =149448499200