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 A188138 #31 Dec 24 2016 22:23:43
%S A188138 1,469,407819,401382971,400757638164,400692683389101,
%T A188138 400686363385965077,400685705322499946270,400685641565621401132515,
%U A188138 400685635084923815073475174,400685634458741808360827818508,400685634393583522561137962683069
%N A188138 Sum of sigma_2(k) for 1 <= k <= 10^n, where sigma_2(k) is the sum of the divisors of k squared.
%C A188138 a(n) ~ 10^(3n)*zeta(3)/3.
%H A188138 Hiroaki Yamanouchi, <a href="/A188138/b188138.txt">Table of n, a(n) for n = 0..18</a>
%t A188138 k = 1; lst = {}; s = 0; Do[ While[k < 10^n + 1, s = s + DivisorSigma[2, k]; k++]; AppendTo[lst, s], {n, 0, 9}]; lst
%t A188138 a[n_] := With[{nn=10^n}, Sum[Floor[nn/k]*k^2, {k, nn}]]; Array[a,9,0] (* _T. D. Noe_, Apr 25 2011 *)
%Y A188138 Cf. A072692.
%K A188138 nonn
%O A188138 0,2
%A A188138 _Robert G. Wilson v_, Apr 25 2011
%E A188138 a(10)-a(11) from _Hiroaki Yamanouchi_, Jul 06 2014