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 A077087 #21 Feb 24 2024 01:04:54
%S A077087 1,1919,2759,11219,27089,50039,58463,100127,113831,115289,120203,
%T A077087 131879,148511,233729,244319,308039,461099,554063,596447,1406303,
%U A077087 1486619,2285519,2880989,5138783,5369111,5521619,5736743,6621383,7496279,7683191,8571527,8848619
%N A077087 Numbers k such that sigma(k+1) = 3 * sigma(k).
%H A077087 Donovan Johnson, <a href="/A077087/b077087.txt">Table of n, a(n) for n = 1..500</a>
%e A077087 k = 1: sigma(2)/sigma(1) = 3/1 = 3;
%e A077087 k = 9563231: sigma(k+1)/sigma(k) = 31026240/10342080 = 3.
%t A077087 Do[s=Mod[a=DivisorSigma[1, n+1], b=DivisorSigma[1, n]]; If[Equal[s, 0]&&Equal[a/b, 3], Print[n]], {n, 1, 10000000}]
%t A077087 Position[Partition[DivisorSigma[1,Range[9*10^6]],2,1],_?(3#[[1]] == #[[2]]&),1,Heads->False]//Flatten (* _Harvey P. Dale_, Oct 03 2017 *)
%Y A077087 Cf. A000203, A002961, A067081, A077086, A272027 (3*sigma(n)).
%K A077087 nonn
%O A077087 1,2
%A A077087 _Labos Elemer_, Oct 31 2002