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 A086898 #6 Dec 12 2017 00:28:44
%S A086898 0,1,2,3,3,5,4,5,6,7,4,9,6,7,9,9,5,11,6,11,12,9,4,13,11,10,10,13,6,17,
%T A086898 8,11,12,10,11,19,9,9,12,17,8,19,8,13,19,11,4,19,14,18,13,16,6,17,15,
%U A086898 19,16,11,4,25,12,11,20,17,16,23,8,14,12,21,8,25,12,12,21,17,14,22,8,23,20
%N A086898 a(n) = Sum_{d|n} tau(d-1).
%H A086898 G. C. Greubel, <a href="/A086898/b086898.txt">Table of n, a(n) for n = 1..10000</a>
%t A086898 a[n_] := DivisorSum[n, If[# == 1, 0, DivisorSigma[0, # - 1]] &]; Array[a, 100] (* _G. C. Greubel_, Dec 11 2017 *)
%Y A086898 Cf. A000005, A049822.
%K A086898 nonn
%O A086898 1,3
%A A086898 _Vladeta Jovovic_, Aug 23 2003