a(n) = Sum_{d|n} phi(d)^(n+1).

Terms

a(0) =1a(1) =2a(2) =17a(3) =34a(4) =4097a(5) =258a(6) =1679617a(7) =262658a(8) =60467201a(9) =8388610a(11) =67133442a(13) =940369969154