This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A077095 #21 May 07 2025 08:17:48
%S A077095 24,42,69,74,75,82,86,94,115,125,133,155,185,187,203,289,299,323,341,
%T A077095 361,377,437,1681
%N A077095 Numbers k such that iterating phi(sigma(k)-phi(k)) starting from k leads to the fixed point 24.
%C A077095 Probably this sequence is finite, with 23 terms of which the last is 1681.
%e A077095 n=1641: FixedPointList={1681,82,42,24}, end=24.
%t A077095 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}]
%t A077095 fp24Q[n_]:=FixedPoint[EulerPhi[DivisorSigma[1,#]-EulerPhi[#]]&,n,20]==24; Select[ Range[1700],fp24Q] (* _Harvey P. Dale_, Mar 12 2023 *)
%Y A077095 Cf. A000010 (phi), A000203 (sigma).
%Y A077095 Cf. A077090, A077091, A077092, A077093, A077094, A077096.
%K A077095 nonn
%O A077095 1,1
%A A077095 _Labos Elemer_, Oct 31 2002