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 A356535 #13 Oct 09 2022 04:23:00
%S A356535 1,26,126,567,1243,3743,6243,13468,21749,38649,53533,97633,126533,
%T A356535 189033,256633,372914,457014,664039,795083,1093199,1343199,1715299,
%U A356535 1996199,2718699,3142500,3865000,4537400,5639900,6348864,8038864,8964308,10827533,12315933,14418433
%N A356535 a(n) = Sum_{k=1..n} sigma_2(k)^2.
%C A356535 Partial sums of A356533.
%H A356535 Amiram Eldar, <a href="/A356535/b356535.txt">Table of n, a(n) for n = 1..10000</a>
%F A356535 a(n) ~ 189 * zeta(3)^2 * zeta(5) * n^5 / Pi^6.
%t A356535 Table[Sum[DivisorSigma[2, k]^2, {k, 1, n}], {n, 1, 40}]
%o A356535 (PARI) a(n) = sum(k=1, n, sigma(k, 2)^2); \\ _Michel Marcus_, Aug 11 2022
%Y A356535 Cf. A001157, A057434, A061502, A072379, A356536.
%Y A356535 Cf. A127473, A035116, A072861, A356533, A356534.
%K A356535 nonn
%O A356535 1,2
%A A356535 _Vaclav Kotesovec_, Aug 11 2022