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

Terms

a(0) =1a(1) =4a(2) =6a(3) =24a(4) =10a(5) =156a(6) =14a(7) =528a(8) =747a(9) =1620a(10) =22a(11) =15000a(12) =26a(13) =12572a(14) =60780a(15) =98336a(16) =34a(17) =397908a(18) =38a(19) =1484840a(20) =1500324a(21) =495660a(22) =46a(23) =18514992a(24) =9765675a(25) =2768948a(26) =28697868a(27) =85098552a(28) =58a(29) =375843660