a(n) = Sum_{d|n} phi(d)^4.

Terms

a(0) =1a(1) =2a(2) =17a(3) =18a(4) =257a(5) =34a(6) =1297a(7) =274a(8) =1313a(9) =514a(10) =10001a(11) =306a(12) =20737a(13) =2594a(14) =4369a(15) =4370a(16) =65537a(17) =2626a(18) =104977a(19) =4626a(20) =22049a(21) =20002a(22) =234257a(23) =4658a(24) =160257a(25) =41474a(26) =106289a(27) =23346a(28) =614657a(29) =8738