login
The OEIS is supported by the many generous donors to the OEIS Foundation.

 

Logo
Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A077095 Starting iteration of Phi[]*(Sigma[]-Phi[]) function at these initial values leads to the fixed point 24. 0
24, 42, 69, 74, 75, 82, 86, 94, 115, 125, 133, 155, 185, 187, 203, 289, 299, 323, 341, 361, 377, 437, 1681 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
Probably this sequence is finite, with 23 terms of which the last is 1681.
LINKS
EXAMPLE
n=1641: FixedPointList={1681,82,42,24},end=24.
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}]
fp24Q[n_]:=FixedPoint[EulerPhi[DivisorSigma[1, #]-EulerPhi[#]]&, n, 20]==24; Select[ Range[1700], fp24Q] (* Harvey P. Dale, Mar 12 2023 *)
CROSSREFS
Sequence in context: A274350 A063702 A074975 * A228844 A111948 A039411
KEYWORD
nonn,fini,full
AUTHOR
Labos Elemer, Oct 31 2002
STATUS
approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified June 24 00:02 EDT 2024. Contains 373661 sequences. (Running on oeis4.)