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

Terms

a(0) =1a(1) =4a(2) =12a(3) =24a(4) =630a(5) =84a(6) =117656a(7) =4176a(8) =531531a(9) =20020a(10) =25937424612a(11) =21192a(13) =15059100a(14) =2562941490a(15) =4295033120a(17) =68025132a(19) =25600320440