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

Terms

a(0) =0a(1) =1a(2) =2a(3) =7a(4) =4a(5) =31a(6) =6a(7) =115a(8) =44a(9) =625a(10) =10a(11) =4597a(12) =12a(13) =35317a(14) =1286a(15) =322891a(16) =16a(17) =3274699a(18) =18a(19) =36290239a(20) =70688a(21) =439084861a(22) =22a(23) =5748677953a(24) =2424a(25) =80951270473a(26) =6532010a(28) =28a(30) =30a(32) =878169812