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 A015706 #20 Aug 09 2021 20:25:45 %S A015706 1,117,135,775,819,891,1521,1701,2325,3159,3375,4455,5733,6875,6975, %T A015706 10935,11907,19773,20625,20925,22113,22275,24025,40131,41067,43875, %U A015706 44375,49005,61875,62775,68607,72075,75625,83349,84375,85293 %N A015706 Odd numbers k that divide phi(k)*sigma(k). %H A015706 Donovan Johnson, <a href="/A015706/b015706.txt">Table of n, a(n) for n = 1..3000</a> %H A015706 Richard K. Guy, <a href="http://www.jstor.org/stable/2974586">Divisors and desires</a>, Amer. Math. Monthly, 104 (1997), 359-360. %t A015706 Select[Range[1,85301,2],Divisible[EulerPhi[#]DivisorSigma[1,#],#]&] (* _Harvey P. Dale_, Aug 27 2013 *) %o A015706 (PARI) isok(n) = (n%2) && !(sigma(n)*eulerphi(n) % n); \\ _Michel Marcus_, Oct 02 2017 %Y A015706 Cf. A011775. %K A015706 nonn %O A015706 1,2 %A A015706 _Robert G. Wilson v_