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 A372709 #18 May 14 2024 05:21:33
%S A372709 1,5,9,18,19,41,31,56,59,83,57,136,73,127,151,170,103,233,119,270,239,
%T A372709 233,151,406,241,285,311,424,205,579,225,464,425,399,473,758,283,459,
%U A372709 517,812,319,891,339,742,853,587,375,1138,571,893,731,920,437,1157,847,1250
%N A372709 a(n) = Sum_{k=1..n} tau(n*k), where tau(n) = number of divisors of n, cf. A000005.
%H A372709 Seiichi Manyama, <a href="/A372709/b372709.txt">Table of n, a(n) for n = 1..10000</a>
%H A372709 Vaclav Kotesovec, <a href="/A372709/a372709.jpg">Plot of a(n) / A372674(n) for n = 1..100000</a>
%F A372709 Conjecture: a(n) ~ A372674(n) / 2. - _Vaclav Kotesovec_, May 13 2024
%t A372709 Table[Sum[DivisorSigma[0, k*n], {k, 1, n}], {n, 1, 50}] (* _Vaclav Kotesovec_, May 13 2024 *)
%o A372709 (PARI) a(n) = sum(k=1, n, numdiv(n*k));
%Y A372709 Cf. A000005, A048691, A263086, A372674, A372710.
%K A372709 nonn
%O A372709 1,2
%A A372709 _Seiichi Manyama_, May 11 2024