a(n) = n! * Sum_{d|n} d^(d - n/d).A351165a(n) = n! * Sum_{d|n} d^(d - n/d).Terms a(0) =1a(1) =6a(2) =60a(3) =1584a(4) =75120a(5) =5601960a(6) =592956000a(7) =84557864160External referencesoeis: A351165