a(n) = n! * (1 + Sum_{k=0..n} (-1)^k * k / k!).

Terms

a(0) =1a(1) =0a(2) =2a(3) =3a(4) =16a(5) =75a(6) =456a(7) =3185a(8) =25488a(9) =229383a(10) =2293840a(11) =25232229a(12) =302786760a(13) =3936227867a(14) =55107190152a(15) =826607852265