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

Terms

a(0) =1a(1) =2a(2) =2a(3) =3a(4) =2a(5) =5a(6) =2a(7) =5a(8) =6a(9) =7a(10) =2a(11) =17a(12) =2a(13) =9a(14) =34a(15) =15a(16) =2a(17) =45a(18) =2a(19) =87a(20) =102a(21) =13a(22) =2a(23) =191a(24) =258a(25) =15a(26) =294a(27) =289a(28) =2a(29) =1579