a(n) = n! * [x^n] Product_{k=1..n, gcd(n,k) = 1} (1 + x^k/k!).

Terms

a(0) =1a(1) =1a(2) =0a(3) =3a(4) =4a(5) =15a(6) =6a(7) =168a(8) =64a(9) =171a(10) =130a(11) =44418a(12) =804a(13) =802750a(14) =2380a(15) =683595a(16) =5782144a(17) =840363295a(18) =40410a(19) =24358246734a(20) =221953840a(21) =3114081516a(22) =5372831860a(24) =25703183400