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 A353683 #7 May 06 2022 15:25:48 %S A353683 2,4,6,8,9,10,12,14,16,18,20,21,22,24,25,28,30,32,34,36,40,42,44,46, %T A353683 48,50,52,54,56,60,62,63,64,66,68,70,72,75,76,78,80,81,84,88,90,92,93, %U A353683 94,96,98,100,102,105,106,108,110,112,114,120,124,126,128,130,132,136,138,140,142,144,148,150,152,154,156,160 %N A353683 Numbers k for which phi(sigma(k)) > phi(k). %C A353683 Numbers k such that A062401(k) > A000010(k). %H A353683 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a> %t A353683 Select[Range[160], EulerPhi[DivisorSigma[1, #]] > EulerPhi[#] &] (* _Amiram Eldar_, May 06 2022 *) %o A353683 (PARI) %o A353683 A353681(n) = (eulerphi(sigma(n))>eulerphi(n)); %o A353683 isA353683(n) = A353681(n); %Y A353683 Positions of strictly positive terms in A353636. %Y A353683 Cf. A000010, A000203, A062401, A353681 (characteristic function), A353685 (complement). %Y A353683 Setwise difference of A353684 and A006872. %K A353683 nonn %O A353683 1,1 %A A353683 _Antti Karttunen_, May 06 2022