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 A384839 #15 Jun 20 2025 18:56:25
%S A384839 93,120,204,211,231,239,254,269,274,280,315,336,343,360,366,372,375,
%T A384839 378,395,396,402,420,466,475,496,592,604,672,708,724,726,774,821,822,
%U A384839 827,836,840,844,845,862,870,880,898,919,926,952,964,976,982,996,997,1023,1077,1080
%N A384839 Numbers k for which sigma(k - x) + sigma(k + x) = 6*k has at least one nonnegative solution.
%H A384839 Michel Marcus, <a href="/A384839/b384839.txt">Table of n, a(n) for n = 1..5000</a>
%t A384839 s={};Do[Do[If[DivisorSigma[1,k-x]+DivisorSigma[1,k+x]==6*k,AppendTo[s,k];Break[]],{x,0,k-1}],{k,1,1080}];s (* _James C. McMahon_, Jun 20 2025 *)
%o A384839 (PARI) isok(k) = for (x=0, k-1, if (sigma(k - x) + sigma(k + x) == 6*k, return(1)));
%Y A384839 Cf. A000203 (sigma), A005820 (a subsequence).
%Y A384839 Cf. A383268, A384838, A384840, A384841.
%Y A384839 Cf. A383758.
%K A384839 nonn
%O A384839 1,1
%A A384839 _Michel Marcus_, Jun 10 2025