Numbers n such that phi(phi(n)) + sigma(sigma(n)) is a 4th power.

Terms

a(0) =9a(1) =42a(2) =101a(3) =339a(4) =407a(5) =420a(6) =471a(7) =915a(8) =1409a(9) =2572a(10) =2847a(11) =3706a(12) =4069a(13) =6631a(14) =6720a(15) =7229a(16) =9212a(17) =14051a(18) =16641a(19) =31453a(20) =33067a(21) =33146a(22) =35701a(23) =37425a(24) =37675a(25) =37911a(26) =48016a(27) =48272a(28) =53101a(29) =55956