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 A363629 #25 Jul 19 2023 02:19:56
%S A363629 -2,1,-6,6,-8,4,-10,15,-16,6,-14,22,-16,8,-28,32,-20,13,-22,32,-36,12,
%T A363629 -26,56,-34,14,-44,42,-32,24,-34,65,-52,18,-52,68,-40,20,-60,82,-44,
%U A363629 32,-46,62,-84,24,-50,122,-60,31,-76,72,-56,40,-76,108,-84,30,-62,124,-64,32,-110,130,-88,48,-70,92
%N A363629 Expansion of Sum_{k>0} (1/(1+x^k)^2 - 1).
%H A363629 Seiichi Manyama, <a href="/A363629/b363629.txt">Table of n, a(n) for n = 1..10000</a>
%F A363629 G.f.: Sum_{k>0} (k+1) * (-x)^k/(1 - x^k).
%F A363629 a(n) = Sum_{d|n} (-1)^d * (d+1) = -(A002129(n) + A048272(n)).
%t A363629 a[n_] := DivisorSum[n, (-1)^#*(# + 1) &]; Array[a, 100] (* _Amiram Eldar_, Jul 18 2023 *)
%o A363629 (PARI) a(n) = sumdiv(n, d, (-1)^d*(d+1));
%Y A363629 Cf. A363630, A363631.
%Y A363629 Cf. A002129, A048272, A325940.
%K A363629 sign,easy
%O A363629 1,1
%A A363629 _Seiichi Manyama_, Jun 12 2023