A096988 Initial values for f(x)=sigma(phi(x))=A062402(x) such that iteration of f ends in cycle of length=1.

1, 2, 3, 4, 6, 13, 15, 16, 20, 21, 23, 24, 25, 26, 28, 30, 33, 36, 42, 44, 46, 50, 66, 157, 169, 203, 215, 237, 241, 245, 255, 256, 261, 272, 275, 287, 303, 305, 314, 316, 320, 325, 338, 340, 344, 347, 367, 369, 375, 384, 385, 392, 393, 404, 406, 408, 429, 430

Offset: 1

Author

Labos Elemer, Jul 19 2004

Keywords

• nonn

Links

• Ivan Neretin, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A062402, A095952, A018784.

Programs

Mathematica

a = {}; Do[s = {n}; While[! MemberQ[s, k = DivisorSigma[1, EulerPhi[s[[-1]]]]], AppendTo[s, k]]; If[s[[-1]] == k, AppendTo[a, n]], {n, 430}]; a (* Ivan Neretin, Dec 15 2016 *)