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 A077091 #14 May 07 2025 05:29:58
%S A077091 4,6,8,9,10,12,14,15,16,18,20,21,22,24,25,26,27,28,30,32,33,34,35,38,
%T A077091 39,42,44,45,46,49,51,54,55,56,57,58,62,63,65,68,69,70,74,75,77,82,85,
%U A077091 86,87,91,93,94,95,99,104,111,115,119,121,125,129,133,134,143,145,153
%N A077091 Composites c, such that when iteration of f(k) = phi(sigma(k)-phi(k)) is started at c it ends at a fixed point > 1.
%e A077091 n=30: FixedPointList={30,32,46,20,16,22,12,8,10,6,4},end=4; n=94:FixedPointList={94,42,24},end=24.
%t A077091 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]&&!PrimeQ[n], Print[{n, s1}]], {n, 1, 1000}]
%Y A077091 Cf. A077090, A077092, A077093, A077094, A077095, A077096.
%K A077091 nonn
%O A077091 1,1
%A A077091 _Labos Elemer_, Oct 31 2002
%E A077091 1 removed by _Sean A. Irvine_, May 05 2025