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 A066930 #25 Apr 27 2025 02:45:49
%S A066930 1,7,9,29,71,97,109,121,139,142,175,183,194,215,225,242,244,261,278,
%T A066930 311,344,349,355,430,497,509,516,533,556,571,605,622,631,647,673,709,
%U A066930 729,791,817,859,911,923,1021,1066,1112,1119,1142,1207,1243,1262,1277
%N A066930 Numbers k such that phi(sigma(k)) divides sigma(phi(k)).
%H A066930 Amiram Eldar, <a href="/A066930/b066930.txt">Table of n, a(n) for n = 1..10000</a> (terms 1..1000 from Harry J. Smith)
%t A066930 Select[Range[1300],Divisible[DivisorSigma[1,EulerPhi[#]],EulerPhi[ DivisorSigma[ 1,#]]]&] (* _Harvey P. Dale_, Dec 15 2021 *)
%o A066930 (PARI) isok(k) = { sigma(eulerphi(k)) % eulerphi(sigma(k)) == 0 } \\ _Harry J. Smith_, Apr 08 2010
%Y A066930 Cf. A000010 (phi), A000203 (sigma), A033632 (subsequence), A062401, A062402.
%K A066930 nonn
%O A066930 1,2
%A A066930 _Benoit Cloitre_, Jan 26 2002