a(n) = n! * Sum_{d|n} 1/((d-1)! * (n/d)^(d-1)).

A370602

a(n) = n! * Sum_{d|n} 1/((d-1)! * (n/d)^(d-1)).

Terms

    a(0) =1a(1) =4a(2) =9a(3) =40a(4) =125a(5) =1056a(6) =5047a(7) =51248a(8) =383049a(9) =4364020a(10) =39916811a(11) =576885552a(12) =6227020813a(13) =99634224704

External references