a(n) = n! * Sum_{d|n} d/(d! * (n/d)!).

Terms

a(0) =1a(1) =3a(2) =4a(3) =17a(4) =6a(5) =307a(6) =8a(7) =5049a(8) =30250a(9) =105851a(10) =12a(11) =25945933a(12) =14a(13) =77837775a(14) =14529715216a(15) =147891744017a(16) =18a(18) =20a(22) =24