a(n) = Sum_{d|n} d * (d!)^(n/d-1).

Terms

a(0) =1a(1) =3a(2) =4a(3) =9a(4) =6a(5) =33a(6) =8a(7) =121a(8) =118a(9) =643a(10) =12a(11) =7349a(12) =14a(13) =35423a(14) =75904a(15) =378129a(16) =18a(17) =6400179a(18) =20a(19) =46256149a(20) =177951190a(21) =439086871a(22) =24a(23) =21025820825a(24) =1036800026a(25) =80951278619a(28) =30a(30) =32