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 A362021 #21 Apr 05 2023 08:28:06
%S A362021 1,-3,0,0,-5,11,-18,18,-18,28,-39,39,-52,66,-51,51,-68,68,-87,87,-66,
%T A362021 88,-111,111,-111,137,-137,137,-166,136,-167,167,-134,168,-133,133,
%U A362021 -170,208,-169,169,-210,168,-211,211,-211,257,-304,304,-304,304,-253,253,-306,306,-251,251,-194,252,-311
%N A362021 a(n) = Sum_{k=1..n} (-1)^(n-k) * k * mu(k), where mu(k) is the Moebius function.
%H A362021 Seiichi Manyama, <a href="/A362021/b362021.txt">Table of n, a(n) for n = 1..10000</a>
%F A362021 G.f.: (Sum_{k>=1} k * mu(k) * x^k) / (1 + x).
%F A362021 G.f. A(x) satisfies x = Sum_{k>=1} k * (1 + x^k) * A(x^k).
%F A362021 a(n) = -a(n-1) + A055615(n) for n > 1.
%o A362021 (PARI) a(n) = sum(k=1, n, (-1)^(n-k)*k*moebius(k));
%Y A362021 Cf. A008683, A055615, A068340, A247418, A361982.
%K A362021 sign,easy,look
%O A362021 1,2
%A A362021 _Seiichi Manyama_, Apr 04 2023