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 A347169 #17 Aug 22 2021 22:15:08 %S A347169 42,3472,56896,544635,234852352,60129083392,962070839296, %T A347169 16140901056979664896,18609191940988822212582848311676895232 %N A347169 Numbers k for which sigma(k)/k = 16/7. %C A347169 This sequence will contain terms of the form 7*P, where P is a perfect number (A000396) not divisible by 7. Proof: sigma(7*P)/(7*P) = sigma(7)*sigma(P)/(7*P) = 8*(2*P)/(7*P) = 16/7. QED %C A347169 Terms ending in "2" or "96" have this form. Example: a(n) = 7*A000396(n) for n = 1, 5, 6, 7, 8, 9 and a(n) = 7*A000396(n+1) for n = 2, 3. %H A347169 G. P. Michon, <a href="http://www.numericana.com/answer/numbers.htm#multiperfect">Multiperfect Numbers and Hemiperfect Numbers</a> %H A347169 Walter Nissen, <a href="http://upforthecount.com/math/abundance.html">Abundancy: Some Resources (preliminary version 4) </a> %H A347169 Walter Nissen, <a href="http://upforthecount.com/math/ffp8.html">Primitive Friendly Pairs with friends < 2^34 with denom < 20000</a> %e A347169 544635 is a term, since sigma(544635)/544635 = 1244880/544635 = 16/7. %t A347169 Select[Range[5*10^8], DivisorSigma[1, #]/# == 16/7 &] %t A347169 Do[If[DivisorSigma[1, k]/k == 16/7, Print[k]], {k, 5*10^8}] %Y A347169 Cf. A000203, A000396. %Y A347169 Subsequence of A005101 and A218409. %K A347169 nonn,more %O A347169 1,1 %A A347169 _Timothy L. Tiffin_, Aug 20 2021 %E A347169 a(8)-a(9) from _Michel Marcus_, Aug 21 2021