Search: id:A077091
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%I A077091
%S A077091 1,4,6,8,9,10,12,14,15,16,18,20,21,22,24,25,26,27,28,30,32,33,34,35,38,
%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 When iteration of f[]=Phi[](Sigma[]-Phi[]) is started at composite initial 
               values listed here it ends at a nonzero fixed point.
%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-A077100.
%Y A077091 Sequence in context: A002808 A018252 A141468 this_sequence A051035 A046349 
               A115683
%Y A077091 Adjacent sequences: A077088 A077089 A077090 this_sequence A077092 A077093 
               A077094
%K A077091 nonn
%O A077091 1,2
%A A077091 Labos E. (labos(AT)ana.sote.hu), Oct 31 2002

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