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 A076723 #12 Dec 22 2018 13:37:38
%S A076723 -1,3,-28,259,-3126,46632,-823544,16777475,-387420517,9999996878,
%T A076723 -285311670612,8916100495144,-302875106592254,11112006824734476,
%U A076723 -437893890380862528,18446744073726329091,-827240261886336764178,39346408075296150201567
%N A076723 Sum_{d divides n} (-d)^d.
%H A076723 Seiichi Manyama, <a href="/A076723/b076723.txt">Table of n, a(n) for n = 1..386</a>
%F A076723 G.f.: Sum_{n>0} (-n*x)^n/(1-x^n).
%o A076723 (PARI) a(n) = sumdiv(n, d, (-d)^d); \\ _Michel Marcus_, Dec 22 2018
%Y A076723 Cf. A062796, A321385.
%K A076723 sign
%O A076723 1,2
%A A076723 _Vladeta Jovovic_, Oct 27 2002