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

Terms

a(0) =1a(1) =2a(2) =17a(3) =34a(4) =4097a(5) =146a(6) =1679617a(7) =262178a(8) =60466193a(9) =4198402a(11) =67109042a(13) =470186664194