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 A174443 #18 Mar 12 2014 16:37:15
%S A174443 0,1,-4,24,-128,704,-3840,20992,-114688,626688,-3424256,18710528,
%T A174443 -102236160,558628864,-3052404736,16678649856,-91133837312,
%U A174443 497964548096,-2720928890880,14867431948288,-81237158920192,443888091267072,-2425449636429824,13252903275855872
%N A174443 Generating function x/(1+4*x-8*x^2).
%C A174443 Binet form: with a = 4/(1 + sqrt(3)); b = 4/(1 - sqrt(3)); we have a(n)=(a^n - b^n)/(a - b).
%C A174443 Alternative expressions for the roots are -2 +- 2*sqrt(3).
%C A174443 Limiting ratio a(n+1)/a(n) is:-5.464101615137755== -2-2*sqrt(3).
%H A174443 Nathaniel Johnston, <a href="/A174443/b174443.txt">Table of n, a(n) for n = 0..500</a>
%F A174443 a(0)=0, a(1)=1, a(n) = -4a(n-1) + 8a(n-2).
%F A174443 a(0)=0, a(n) = (-2)^(n-1)*A002605(n).
%t A174443 a = 4/(1 + Sqrt[3]); b = 4/(1 - Sqrt[3]);
%t A174443 f[n_] = (a^n - b^n)/(a - b);
%t A174443 Table[FullSimplify[f[n]], {n, 0, 30}]
%Y A174443 Cf. A180222 (unsigned version of this sequence).
%K A174443 sign,easy
%O A174443 0,3
%A A174443 _Roger L. Bagula_, Nov 28 2010
%E A174443 Correction of the Mathematica code and better name by _Joerg Arndt_.
%E A174443 Formulae and edited by _Ralf Stephan_, Nov 27 2010