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

Terms

a(0) =1a(1) =2a(2) =2a(3) =3a(4) =2a(5) =5a(6) =2a(7) =5a(8) =5a(9) =11a(10) =2a(11) =12a(12) =2a(13) =35a(14) =34a(15) =15a(16) =2a(17) =44a(18) =2a(19) =80a(20) =252a(21) =515a(22) =2a(23) =56a(24) =127a(25) =2051a(26) =254a(27) =1066a(28) =2a(29) =389