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 A209243 #14 Jan 08 2018 09:43:44
%S A209243 0,1,6,25,88,285,882,2661,7916,23381,68850,202621,596768,1760289,
%T A209243 5201854,15401317,45682536,135728009,403864570,1203278513,3589064828,
%U A209243 10715405153,32017223498,95730557865,286392391568,857187336029
%N A209243 3^n times the expected value of the shortest run of 0's in a length n word on alphabet {0,1,2}.
%D A209243 R. Sedgewick and P. Flajolet, Analysis of Algorithms, Addison and Wesley, 1996, Chapter 7
%H A209243 G. C. Greubel, <a href="/A209243/b209243.txt">Table of n, a(n) for n = 0..1000</a>
%F A209243 O.g.f.: Sum_{k=1..n} x^k/((1 - 2x)*(1 - 3x + 2x^2 - 2x^(k+1)))
%t A209243 nn=25; a=x^k/(1-x); CoefficientList[Series[Sum[(a+1)/(1-(2x a)/(1-2x))/(1-2x)-1/(1-2x), {k,1,nn}], {x,0,nn}], x]
%Y A209243 Cf. A209232.
%K A209243 nonn
%O A209243 0,3
%A A209243 _Geoffrey Critzer_, Jan 13 2013