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

Terms

a(0) =1a(1) =2a(2) =5a(3) =6a(4) =17a(5) =14a(6) =37a(7) =26a(8) =53a(9) =82a(10) =101a(11) =74a(12) =145a(13) =254a(14) =385a(15) =162a(16) =257a(17) =398a(18) =325a(19) =1218a(20) =1697a(21) =1102a(22) =485a(23) =1058a(24) =4497a(25) =1874a(26) =2645a(27) =8394a(28) =785a(29) =19330