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 A333810 #4 Apr 05 2020 23:28:25
%S A333810 0,1,1,1,1,-1,1,-1,1,-1,1,2,1,-1,4,-1,1,2,1,-5,4,-1,1,-2,1,-1,4,-5,1,
%T A333810 7,1,-5,4,-1,6,-2,1,-1,4,0,1,-4,1,-5,9,-1,1,-8,1,4,4,-5,1,-4,6,2,4,-1,
%U A333810 1,-3,1,-1,11,-5,6,-4,1,-5,4,11,1,-16,1,-1,9,-5,8,-4,1,-8
%N A333810 G.f.: Sum_{k>=1} (-1)^(k + 1) * k * x^(k*(k + 1)) / (1 - x^k).
%C A333810 Excess of sum of odd divisors of n that are < sqrt(n) over sum of even divisors of n that are < sqrt(n).
%t A333810 nmax = 80; CoefficientList[Series[Sum[(-1)^(k + 1) k x^(k (k + 1))/(1 - x^k), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
%Y A333810 Cf. A002129, A070039, A333782, A333807, A333809.
%K A333810 sign
%O A333810 1,12
%A A333810 _Ilya Gutkovskiy_, Apr 05 2020