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

Terms

a(0) =0a(1) =0a(2) =2a(3) =9a(4) =40a(5) =205a(6) =1236a(7) =8659a(8) =69280a(9) =623529a(10) =6235300a(11) =68588311a(12) =823059744a(13) =10699776685a(14) =149796873604