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A293711 Numbers k such that phi(sigma(k))/k < phi(sigma(m))/m for all m < k, where sigma is the sum of divisors function (A000203) and phi is Euler's totient function (A000010). 1

%I #10 Sep 07 2023 12:50:30

%S 1,3,5,11,17,23,29,59,89,149,179,239,269,359,377,389,419,839,1049,

%T 1259,1889,2099,2309,9239,11549,13859,20789,23099,25409,30029,90089,

%U 180179,210209,270269,300299,330329,390389,420419,540539,570569,1017917,1018013,1021019

%N Numbers k such that phi(sigma(k))/k < phi(sigma(m))/m for all m < k, where sigma is the sum of divisors function (A000203) and phi is Euler's totient function (A000010).

%H Amiram Eldar, <a href="/A293711/b293711.txt">Table of n, a(n) for n = 1..127</a>

%t a={}; rm=2; Do[r=EulerPhi[DivisorSigma[1,n]]/n; If[r<rm, rm=r; AppendTo[a,n]], {n,1,100000}];a

%Y Cf. A000010, A000203, A062401.

%K nonn

%O 1,2

%A _Amiram Eldar_, Oct 15 2017

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Last modified April 24 22:17 EDT 2024. Contains 371964 sequences. (Running on oeis4.)