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 A384838 #12 Jun 12 2025 09:08:57 %S A384838 24,53,56,63,66,74,75,79,82,84,95,112,168,192,216,227,245,252,255,274, %T A384838 280,282,288,308,312,347,348,351,360,365,392,395,408,420,431,432,434, %U A384838 458,465,466,471,476,496,528,532,560,576,579,588,624,628,644,670,694,716,720,784 %N A384838 Numbers k for which sigma(k - x) + sigma(k + x) = 5*k has at least one nonnegative solution. %H A384838 Michel Marcus, <a href="/A384838/b384838.txt">Table of n, a(n) for n = 1..5000</a> %o A384838 (PARI) isok(k) = for (x=0, k-1, if (sigma(k - x) + sigma(k + x) == 5*k, return(1))); %Y A384838 Cf. A000203 (sigma), A141643 (a subsequence). %Y A384838 Cf. A383268, A384839, A384840, A384841. %Y A384838 Cf. A383758. %K A384838 nonn %O A384838 1,1 %A A384838 _Michel Marcus_, Jun 10 2025