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 A353684 #7 May 06 2022 15:26:10 %S A353684 1,2,3,4,6,8,9,10,12,14,15,16,18,20,21,22,24,25,26,28,30,32,34,36,39, %T A353684 40,42,44,45,46,48,50,52,54,56,60,62,63,64,66,68,70,72,74,75,76,78,80, %U A353684 81,84,88,90,92,93,94,96,98,100,102,104,105,106,108,110,111,112,114,117,120,122,124,126,128,130,132,136,138 %N A353684 Numbers k for which phi(sigma(k)) >= phi(k). %C A353684 Numbers k such that A062401(k) >= A000010(k). %H A353684 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a> %t A353684 Select[Range[140], EulerPhi[DivisorSigma[1, #]] >= EulerPhi[#] &] (* _Amiram Eldar_, May 06 2022 *) %o A353684 (PARI) %o A353684 A353682(n) = (eulerphi(sigma(n))>=eulerphi(n)); %o A353684 isA353684(n) = A353682(n); %Y A353684 Positions of nonnegative terms in A353636. %Y A353684 Cf. A000010, A000203, A062401, A353682 (characteristic function), A353686 (complement). %Y A353684 Disjoint union of A006872 and A353683. %K A353684 nonn %O A353684 1,2 %A A353684 _Antti Karttunen_, May 06 2022