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 A015759 #26 Jan 08 2025 12:46:47
%S A015759 1,2,3,6,22,33,66,750,27798250,41697375,76745867,83394750,153491734,
%T A015759 207656250,230237601,460475202,917342250,969062500,2907187500,
%U A015759 4528006153,5952812500,9056012306,13584018459,17858437500,27168036918,31979062500,57559400250
%N A015759 Numbers k such that phi(k) | sigma_2(k).
%C A015759 sigma_2(k) is the sum of the squares of the divisors of k (A001157).
%C A015759 All of these terms are solutions to relations for all j as follows: {sigma(j,x)/phi(x) is an integer for exponents j=4k+2}. Proof is possible by individual managements in the knowledge of divisors of x and phi(x). Compare with A015765, A015768, etc. - _Labos Elemer_, May 25 2004
%t A015759 Do[ If[ IntegerQ[ DivisorSigma[2, n]/EulerPhi[n]], Print[n]], {n, 1, 10^7}]
%t A015759 Empirical test for very high power sums of divisors [e.g., d^2802]. Table[{4*j+2, Union[Table[IntegerQ[DivisorSigma[4*j+2, Part[t, k]]/EulerPhi[Part[t, k]]], {k, 1, 13}]]}, {j, 0, 700}] Output = {True} for all 4j+2. Here t=A015759. (* _Labos Elemer_, May 20 2004 *)
%Y A015759 Cf. A000010, A001157, A093643.
%Y A015759 Cf. A015765, A015768, A094470.
%K A015759 nonn
%O A015759 1,2
%A A015759 _Robert G. Wilson v_
%E A015759 a(9)-a(13) from _Labos Elemer_, May 20 2004
%E A015759 a(14)-a(18) from _Donovan Johnson_, Feb 05 2010
%E A015759 a(19)-a(27) from _Donovan Johnson_, Jun 18 2011