A096888 Initial values for f(x)=phi(sigma(x)) such that iteration of f ends in cycle of length=11.

76050, 88452, 88896, 95922, 104364, 104988, 106032, 108252, 110450, 110928, 112896, 113052, 113412, 113868, 115572, 119892, 119916, 121680, 122220, 122832, 122916, 123060, 123312, 129600, 129840, 129984, 130260, 130560, 131280, 133860

Offset

1,1

Links

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

Mathematica

g[n_] := EulerPhi[ DivisorSigma[1, n]]; f[n_] := f[n] = Block[{lst = NestWhileList[g, n, UnsameQ, All ]}, -Subtract @@ Flatten[ Position[lst, lst[[ -1]]]]]; Select[ Range[134000], f[ # ] == 11 &]

Prog

(PARI) f(x, k=1)=for(i=1, k, x=eulerphi(sigma(x))); x
is(n)=my(t=f(n), h=f(t)); while(t!=h, t=f(t); h=f(f(h))); h=f(h); t!=h && t==f(h, 10) \\ Charles R Greathouse IV, Nov 25 2013

Crossrefs

Cf. A000010, A000203, A095952, A096887, A095953, A096526, A095954, A096889, A096890, A095955, A095956.

Sequence in context: A091294 A096518 A234895 * A049026 A187424 A186216

Adjacent sequences: A096885 A096886 A096887 * A096889 A096890 A096891

Keyword

nonn

Author

Labos Elemer and Robert G. Wilson v, Jul 14 2004

Status

approved