a(n) = n! * Sum_{k=0..n-2} 1/k!.

Terms

a(0) =0a(1) =0a(2) =2a(3) =12a(4) =60a(5) =320a(6) =1950a(7) =13692a(8) =109592a(9) =986400a(10) =9864090a(11) =108505100a(12) =1302061332a(13) =16926797472a(14) =236975164790