Number of lucky numbers <= n!.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =7a(5) =26a(6) =115a(7) =614a(8) =3866a(9) =28339a(10) =237017a(11) =2227657a(12) =23233568a(13) =266201749