a(n) = Sum_{k=1..n} phi(gcd(k, n))^(n/gcd(k, n) - 1).

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =5a(5) =7a(6) =7a(7) =9a(8) =15a(9) =13a(10) =11a(11) =33a(12) =13a(13) =19a(14) =105a(15) =33a(16) =17a(17) =91a(18) =19a(19) =209a(20) =469a(21) =31a(22) =23a(23) =641a(24) =1045a(25) =37a(26) =1627a(27) =841a(28) =29a(29) =4217