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 A372833 #12 Jan 27 2025 18:39:11
%S A372833 1,1,1,2,1,2,1,2,3,2,1,6,1,2,3,4,1,6,1,4,3,2,1,12,5,2,3,4,1,30,1,4,3,
%T A372833 2,5,4,1,2,3,20,1,1,1,4,15,2,1,4,7,10,3,4,1,1,5,28,3,2,1,20,1,2,21,8,
%U A372833 5,1,1,4,3,70,1,8,1,2,15,4,7,1,1,40
%N A372833 a(n) is the denominator of Sum_{d|n, d <= sqrt(n)} 1/d.
%C A372833 a(n) is a divisor of A072504(n). The first few values of n for which a(n) != A072504(n) are 36, 42, 48, 54, 60, 66, 72, 78, 84, 90, 96, 102, 110, ... . - _Pontus von Brömssen_, May 15 2024
%H A372833 Antti Karttunen, <a href="/A372833/b372833.txt">Table of n, a(n) for n = 1..20000</a>
%F A372833 Denominators of coefficients in expansion of Sum_{k>=1} x^(k^2) / (k * (1 - x^k)).
%e A372833 1, 1, 1, 3/2, 1, 3/2, 1, 3/2, 4/3, 3/2, 1, 11/6, 1, 3/2, 4/3, 7/4, 1, 11/6, ...
%t A372833 nmax = 80; CoefficientList[Series[Sum[x^(k^2)/(k (1 - x^k)), {k, 1, nmax}], {x, 0, nmax}], x] // Denominator // Rest
%o A372833 (PARI) a(n) = denominator(sumdiv(n, d, if (d^2 <= n, 1/d))); \\ _Michel Marcus_, May 14 2024
%Y A372833 Cf. A017666, A066839, A072504, A372832 (numerators).
%K A372833 nonn,frac
%O A372833 1,4
%A A372833 _Ilya Gutkovskiy_, May 14 2024