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%I #10 Dec 12 2024 15:12:59
%S 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 71,73,79,82,83,85,86,89,94,95,97,101,103,106,107,109,113,115,118,122,
%U 125,131,134,137,139,142,145,146,149,151,157,163,166,167,170,173
%N 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 Paolo Xausa, <a href="/A378915/b378915.txt">Table of n, a(n) for n = 1..10000</a>
%H <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%t With[{upto = 500}, Table[If[Count[Divisible[n, #[[;; n]]], True] == 1, n, Nothing], {n, upto}] & [DivisorSigma[1, Range[upto]]]]
%o (PARI) isok(m) = for(k=2, m, if (!(m % sigma(k)), return(0))); 1; \\ _Michel Marcus_, Dec 12 2024
%Y Positions of ones in A378913.
%Y Cf. A000203.
%K nonn,new
%O 1,2
%A _Paolo Xausa_, Dec 11 2024