a(n) = n! * Sum_{k=0..n} k^(k*(n-k))/k!.

A356674

a(n) = n! * Sum_{k=0..n} k^(k*(n-k))/k!.

Terms

    a(0) =1a(1) =2a(2) =5a(3) =25a(4) =349a(5) =19941a(6) =4440391a(7) =4382699203

External references