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A077094 Starting the iteration of the function Phi[(Sigma[]-Phi[])] at these initial values leads to the fixed point 4. 0
4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 22, 25, 26, 27, 28, 30, 32, 33, 34, 35, 38, 39, 44, 45, 46, 49, 51, 54, 55, 56, 57, 58, 62, 63, 65, 68, 70, 77, 85, 87, 91, 93, 95, 99, 104, 111, 119, 121, 129, 134, 143, 145, 153, 158, 161, 169, 189, 205, 209, 215, 221, 245 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Probably this sequence is finite, with 92 terms of which the last is 6241.
LINKS
EXAMPLE
n=6241: FixedPointList={6241,104,54,32,20,16,22,12,8,10,6,4},end=4.
MATHEMATICA
f[x_] := EulerPhi[DivisorSigma[1, x]-EulerPhi[x]] Do[s=NestList[f, n, 100]; s1=Part[s, 99]; s2=Part[s, 100]; If[Equal[s1, s2]&&Equal[s1, 4], Print[{n, s1}]], {n, 1, 1000000}]
f4[n_]:=FixedPoint[EulerPhi[DivisorSigma[1, #]-EulerPhi[#]]&, n, 50]==4; Select[Range[250], f4] (* Harvey P. Dale, May 01 2021 *)
CROSSREFS
Sequence in context: A192506 A091212 A205783 * A210441 A343597 A199009
KEYWORD
nonn,fini
AUTHOR
Labos Elemer, Oct 31 2002
EXTENSIONS
Definition corrected by Harvey P. Dale, May 01 2021
STATUS
approved

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Last modified May 27 02:41 EDT 2024. Contains 372847 sequences. (Running on oeis4.)