%I #11 Apr 16 2024 02:40:07

%S 2,3,5,7,13,31,37,61,181,241,421,1009,1201,1321,1801,2161,2521,7561,

%T 12601,15121,30241,55441,110881,278263,332641,555911,666917,722473,

%U 1443853,2165407,3607403,4324321,7212581,8654539,10817761,21631147,36768847,43243201,61276871

%N Numbers k > 1 such that sigma(phi(k))/sigma(k) > sigma(phi(j))/sigma(j) for all 1 < j < k.

%C Without the restrictions k > 1 and j > 1, 1 will be a term instead of 2 and 3. - _Amiram Eldar_, Apr 16 2024

%H Amiram Eldar, <a href="/A067573/b067573.txt">Table of n, a(n) for n = 1..53</a>

%t a = 0; Do[b = DivisorSigma[1, EulerPhi[n]]/DivisorSigma[1, n]; If[b > a, a = b; Print[n]], {n, 2, 10^7}]

%o (PARI) lista(kmax) = {my(rm = 0, f); for(k = 2, kmax, f = factor(k); r = sigma(eulerphi(f)) / sigma(f); if(r > rm, rm = r; print1(k, ", ")));} \\ _Amiram Eldar_, Apr 16 2024

%Y Cf. A000010 (phi), A000203 (sigma), A062402.

%K nonn

%O 1,1

%A _Robert G. Wilson v_, Jan 30 2002

%E a(37)-a(39) added and name corrected by _Amiram Eldar_, Apr 16 2024