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 A378915 #10 Dec 12 2024 15:12:59
%S A378915 1,2,5,10,11,17,19,22,23,25,29,34,37,41,43,46,47,50,53,55,58,59,61,67,
%T A378915 71,73,79,82,83,85,86,89,94,95,97,101,103,106,107,109,113,115,118,122,
%U A378915 125,131,134,137,139,142,145,146,149,151,157,163,166,167,170,173
%N A378915 Positive integers k such that k is not divisible by sigma(m) for any m >= 2, where sigma is the sum-of-divisors function (A000203).
%H A378915 Paolo Xausa, <a href="/A378915/b378915.txt">Table of n, a(n) for n = 1..10000</a>
%H A378915 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%t A378915 With[{upto = 500}, Table[If[Count[Divisible[n, #[[;; n]]], True] == 1, n, Nothing], {n, upto}] & [DivisorSigma[1, Range[upto]]]]
%o A378915 (PARI) isok(m) = for(k=2, m, if (!(m % sigma(k)), return(0))); 1; \\ _Michel Marcus_, Dec 12 2024
%Y A378915 Positions of ones in A378913.
%Y A378915 Cf. A000203.
%K A378915 nonn
%O A378915 1,2
%A A378915 _Paolo Xausa_, Dec 11 2024