a(n) = n! * (1 + Sum_{k=0..n} k^3 / k!).

Terms

a(0) =1a(1) =2a(2) =12a(3) =63a(4) =316a(5) =1705a(6) =10446a(7) =73465a(8) =588232a(9) =5294817a(10) =52949170a(11) =582442201a(12) =6989308140a(13) =90861008017