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 A372835 #7 May 18 2024 02:23:19
%S A372835 1,1,1,1,1,2,1,2,1,2,1,6,1,2,3,2,1,6,1,4,3,2,1,12,1,2,3,4,1,30,1,4,3,
%T A372835 2,5,12,1,2,3,20,1,1,1,4,15,2,1,4,1,10,3,4,1,1,5,28,3,2,1,20,1,2,21,4,
%U A372835 5,1,1,4,3,70,1,8,1,2,15,4,7,1,1,40
%N A372835 a(n) is the denominator of Sum_{d|n, d < sqrt(n)} 1/d.
%F A372835 Denominators of coefficients in expansion of Sum_{k>=1} x^(k*(k+1)) / (k * (1 - x^k)).
%e A372835 0, 1, 1, 1, 1, 3/2, 1, 3/2, 1, 3/2, 1, 11/6, 1, 3/2, 4/3, 3/2, 1, 11/6, ...
%t A372835 nmax = 80; CoefficientList[Series[Sum[x^(k (k + 1))/(k (1 - x^k)), {k, 1, nmax}], {x, 0, nmax}], x] // Denominator // Rest
%o A372835 (PARI) a(n) = denominator(sumdiv(n, d, if (d^2 < n, 1/d))); \\ _Michel Marcus_, May 14 2024
%Y A372835 Cf. A017666, A070039, A372834 (numerators).
%K A372835 nonn,frac
%O A372835 1,6
%A A372835 _Ilya Gutkovskiy_, May 14 2024