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 A378913 #12 Dec 12 2024 15:12:39
%S A378913 1,1,3,4,1,8,5,11,3,1,1,28,10,18,11,11,1,35,1,23,7,1,1,87,1,10,3,33,1,
%T A378913 45,42,63,3,1,5,77,1,38,30,57,1,112,1,47,11,1,1,202,5,1,3,13,1,122,1,
%U A378913 107,52,1,1,205,1,103,39,63,10,8,1,71,3,18,1,389,1,74,11
%N A378913 a(n) = sum of all positive m such that sigma(m) divides n, where sigma is the sum-of-divisors function (A000203).
%H A378913 Paolo Xausa, <a href="/A378913/b378913.txt">Table of n, a(n) for n = 1..10000</a>
%H A378913 <a href="/index/Si#SIGMAN">Index entries for sequences related to sigma(n)</a>
%t A378913 With[{nmax = 100}, Table[Total[PositionIndex[Divisible[n, #[[;; n]]]][True]], {n, nmax}] & [DivisorSigma[1, Range[nmax]]]]
%o A378913 (PARI) a(n) = vecsum(select(x->(!(n % sigma(x))), [1..n])); \\ _Michel Marcus_, Dec 11 2024
%Y A378913 Row sums of A378912.
%Y A378913 Cf. A378915 (positions of ones).
%Y A378913 Cf. A000203.
%K A378913 nonn
%O A378913 1,3
%A A378913 _Paolo Xausa_, Dec 11 2024