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

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =10a(5) =26a(6) =276a(7) =1212a(8) =14736a(9) =92304a(10) =1285920a(11) =10516320a(12) =166112640a(13) =1680462720a(14) =29753498880a(15) =359124192000