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 A348954 #9 Dec 14 2021 12:10:22
%S A348954 0,1,-1,1,-1,-1,-1,3,-1,-1,-1,6,-1,-1,-4,3,-1,2,-1,-1,-4,-1,-1,10,-1,
%T A348954 -1,-4,-1,-1,7,-1,7,-4,-1,-6,2,-1,-1,-4,12,-1,-4,-1,-1,-9,-1,-1,16,-1,
%U A348954 4,-4,-1,-1,-4,-6,14,-4,-1,-1,13,-1,-1,-11,7,-6,-4,-1,-1,-4,11,-1,8,-1,-1,-9,-1,-8,-4,-1,20
%N A348954 a(n) = Sum_{d|n, d < sqrt(n)} (-1)^(n/d) * d.
%H A348954 Antti Karttunen, <a href="/A348954/b348954.txt">Table of n, a(n) for n = 1..20000</a>
%F A348954 G.f.: Sum_{k>=1} (-1)^(k + 1) * k * x^(k*(k + 1)) / (1 + x^k).
%t A348954 Table[DivisorSum[n, (-1)^(n/#) # &, # < Sqrt[n] &], {n, 1, 80}]
%t A348954 nmax = 80; CoefficientList[Series[Sum[(-1)^(k + 1) k x^(k (k + 1))/(1 + x^k), {k, 1, nmax}], {x, 0, nmax}], x] // Rest
%o A348954 (PARI) A348954(n) = sumdiv(n,d,if((d*d)<n,d*(-1)^(n/d),0)); \\ _Antti Karttunen_, Nov 05 2021
%Y A348954 Cf. A000593, A070039, A109506, A333810, A348660, A348951, A348952, A348953, A348955, A348956.
%K A348954 sign
%O A348954 1,8
%A A348954 _Ilya Gutkovskiy_, Nov 04 2021