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

A354862

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

Terms

    a(0) =1a(1) =5a(2) =37a(3) =601a(4) =14401a(5) =520801a(6) =25401601a(7) =1626189601a(8) =131682257281

External references