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 A067704 #13 Oct 15 2020 15:51:58 %S A067704 2,6,8,9,24,28,70,78,128,140,222,234,280,312,350,366,384,438,496,525, %T A067704 666,864,888,910,918,936,942,1036,1098,1158,1232,1314,1400,1464,1575, %U A067704 1662,1708,1752,1824,1836,1878,1900,1938,2044,2382,2480,2526,2590,2664 %N A067704 Numbers n such that phi(sigma(n)) = 2*phi(n). %H A067704 M. F. Hasler and Charles R Greathouse IV, <a href="/A067704/b067704.txt">Table of n, a(n) for n = 1..10000</a> (first 110 terms from Hasler) %t A067704 Select[Range[3000],EulerPhi[DivisorSigma[1,#]]==2EulerPhi[#]&] (* _Harvey P. Dale_, Oct 15 2020 *) %o A067704 (PARI) is(n)=2*eulerphi(n=factor(n))==eulerphi(sigma(n)) \\ _Charles R Greathouse IV_, Nov 27 2013 %Y A067704 Cf. A137815, A137816. %K A067704 nonn %O A067704 1,1 %A A067704 _Benoit Cloitre_, Feb 05 2002