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 A067573 #11 Apr 16 2024 02:40:07
%S A067573 2,3,5,7,13,31,37,61,181,241,421,1009,1201,1321,1801,2161,2521,7561,
%T A067573 12601,15121,30241,55441,110881,278263,332641,555911,666917,722473,
%U A067573 1443853,2165407,3607403,4324321,7212581,8654539,10817761,21631147,36768847,43243201,61276871
%N A067573 Numbers k > 1 such that sigma(phi(k))/sigma(k) > sigma(phi(j))/sigma(j) for all 1 < j < k.
%C A067573 Without the restrictions k > 1 and j > 1, 1 will be a term instead of 2 and 3. - _Amiram Eldar_, Apr 16 2024
%H A067573 Amiram Eldar, <a href="/A067573/b067573.txt">Table of n, a(n) for n = 1..53</a>
%t A067573 a = 0; Do[b = DivisorSigma[1, EulerPhi[n]]/DivisorSigma[1, n]; If[b > a, a = b; Print[n]], {n, 2, 10^7}]
%o A067573 (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 A067573 Cf. A000010 (phi), A000203 (sigma), A062402.
%K A067573 nonn
%O A067573 1,1
%A A067573 _Robert G. Wilson v_, Jan 30 2002
%E A067573 a(37)-a(39) added and name corrected by _Amiram Eldar_, Apr 16 2024