a(n) = n! * Sum_{k=0..n} k^(k*n)/k!.A356689a(n) = n! * Sum_{k=0..n} k^(k*n)/k!.Terms a(0) =1a(1) =2a(2) =20a(3) =19887a(4) =4297096180External referencesoeis: A356689