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 A333782 #8 Apr 06 2020 00:17:55
%S A333782 1,1,1,-1,1,-1,1,-1,4,-1,1,2,1,-1,4,-5,1,2,1,-5,4,-1,1,-2,6,-1,4,-5,1,
%T A333782 7,1,-5,4,-1,6,-8,1,-1,4,0,1,-4,1,-5,9,-1,1,-8,8,4,4,-5,1,-4,6,2,4,-1,
%U A333782 1,-3,1,-1,11,-13,6,-4,1,-5,4,11,1,-16,1,-1,9,-5,8,-4,1,-8
%N A333782 G.f.: Sum_{k>=1} (-1)^(k + 1) * k * x^(k^2) / (1 - x^k).
%C A333782 Excess of sum of odd divisors of n that are <= sqrt(n) over sum of even divisors of n that are <= sqrt(n).
%t A333782 nmax = 80; CoefficientList[Series[Sum[(-1)^(k + 1) k x^(k^2)/(1 - x^k), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
%o A333782 (PARI) a(n) = sumdiv(n, d, if (d^2<=n, if (d%2, d, -d))); \\ _Michel Marcus_, Apr 05 2020
%Y A333782 Cf. A002129, A066839, A069289, A333781.
%K A333782 sign
%O A333782 1,9
%A A333782 _Ilya Gutkovskiy_, Apr 05 2020