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 A153366 #15 May 18 2025 19:35:59 %S A153366 5,16,56,200,720,2600,9400,34000,123000,445000,1610000,5825000, %T A153366 21075000,76250000,275875000,998125000,3611250000,13065625000, %U A153366 47271875000,171031250000,618796875000,2238828125000,8100156250000,29306640625000 %N A153366 Number of zig-zag paths from top to bottom of a rectangle of width 9 with 2*n-1 rows whose color is that of the top right corner. %H A153366 Joseph Myers, <a href="http://www.polyomino.org.uk/publications/2008/bmo1-2009-q1.pdf">BMO 2008--2009 Round 1 Problem 1---Generalisation</a> %F A153366 Empirical G.f.: x*(5-9*x+x^2)/(1-5*x+5*x^2). - _Colin Barker_, Jan 04 2012 %Y A153366 Cf. A153362, A153363, A153364, A153365, A153367. %K A153366 nonn,easy %O A153366 1,1 %A A153366 _Joseph Myers_, Dec 24 2008