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 A015761 #12 Jun 23 2019 13:15:18 %S A015761 1,2,3,6,12,14,15,30,35,38,42,54,56,70,78,87,95,105,114,126,135,140, %T A015761 147,168,174,182,190,209,210,215,216,222,248,258,264,270,285,294,297, %U A015761 315,357,418,420,430,455,456,540,546,551,570,594,609,616,627 %N A015761 Numbers k such that phi(k) | sigma_3(k). %C A015761 sigma_3(k) is the sum of the cubes of the divisors of k (A001158). %H A015761 Amiram Eldar, <a href="/A015761/b015761.txt">Table of n, a(n) for n = 1..10000</a> %t A015761 Select[Range[630], Divisible[DivisorSigma[3, #], EulerPhi[#]] &] (* _Amiram Eldar_, Jun 23 2019 *) %o A015761 (PARI) isok(k) = (sigma(k, 3) % eulerphi(k)) == 0; \\ _Michel Marcus_, Jun 23 2019 %Y A015761 Cf. A000010, A001158. %K A015761 nonn %O A015761 1,2 %A A015761 _Robert G. Wilson v_