a(n) = n! * Sum_{k=1..n-2} 1/k!.

Terms

a(0) =0a(1) =0a(2) =0a(3) =6a(4) =36a(5) =200a(6) =1230a(7) =8652a(8) =69272a(9) =623520a(10) =6235290a(11) =68588300a(12) =823059732a(13) =10699776672a(14) =149796873590