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A289125
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Numbers n such that phi(n)/phi(phi(n)) > phi(m)/phi(phi(m)) for all m < n.
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1
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1, 3, 7, 31, 211, 2311, 43891, 60653, 870871, 1023053, 13123111, 19417793, 300690391, 446235509, 6915878971, 12939711677, 200560490131
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OFFSET
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1,2
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COMMENTS
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Erdős et al. proved that phi(n)/phi(phi(n)) is unbounded, thus this sequence is infinite.
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LINKS
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MATHEMATICA
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a = {}; k=1; rmax = 0; While[Length[a]<10, s = EulerPhi[ k]; s2 = EulerPhi[ s]; r = s/s2; If[r > rmax, AppendTo[a, k]; rmax = r]; k++]; a
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PROG
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(PARI) r=0; forfactored(n=1, 10^10, t=eulerphi(n); t/=eulerphi(t); if(t>r, r=t; print1(n[1]", "))) \\ Charles R Greathouse IV, Jun 25 2017
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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