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 A353686 #6 May 06 2022 15:26:16 %S A353686 5,7,11,13,17,19,23,27,29,31,33,35,37,38,41,43,47,49,51,53,55,57,58, %T A353686 59,61,65,67,69,71,73,77,79,82,83,85,86,87,89,91,95,97,99,101,103,107, %U A353686 109,113,115,116,118,119,121,123,125,127,129,131,133,134,135,137,139,141,143,145,147,149,151,153,155,157,158,159 %N A353686 Numbers k for which phi(sigma(k)) < phi(k). %C A353686 Numbers k such that A062401(k) < A000010(k). %H A353686 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a> %t A353686 Select[Range[160], EulerPhi[DivisorSigma[1, #]] < EulerPhi[#] &] (* _Amiram Eldar_, May 06 2022 *) %o A353686 (PARI) isA353686(n) = (eulerphi(sigma(n))<eulerphi(n)); %Y A353686 Cf. A000010, A000203, A062401, A353684 (complement). %Y A353686 Positions of terms < 0 in A353636. Positions of zeros in A353682. %Y A353686 Setwise difference of A353685 and A006872. %K A353686 nonn %O A353686 1,1 %A A353686 _Antti Karttunen_, May 06 2022