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 A239265 #21 Jul 15 2023 17:55:30 %S A239265 1,5,43,451,4945,54685,605707,6710971,74358721,823915861,9129240139, %T A239265 101154812563,1120826772817,12419109262381,137607593744107, %U A239265 1524734943844939,16894537473570817,187196730554444581,2074198005431257579,22982759116542299875 %N A239265 Number of domicule tilings of a 3 X 2n grid. %C A239265 A domicule is either a domino or it is formed by the union of two neighboring unit squares connected via their corners. In a tiling the connections of two domicules are allowed to cross each other. %H A239265 Alois P. Heinz, <a href="/A239265/b239265.txt">Table of n, a(n) for n = 0..950</a> %H A239265 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (13,-21,-3). %F A239265 G.f.: -(x^2+8*x-1)/(3*x^3+21*x^2-13*x+1). %e A239265 a(1) = 5: %e A239265 +---+ +---+ +---+ +---+ +---+ %e A239265 |o o| |o o| |o-o| |o-o| |o-o| %e A239265 | X | || || | | | | | | %e A239265 |o o| |o o| |o-o| |o o| |o o| %e A239265 | | | | | | || || | X | %e A239265 |o-o| |o-o| |o-o| |o o| |o o| %e A239265 +---+ +---+ +---+ +---+ +---+. %p A239265 gf:= -(x^2+8*x-1)/(3*x^3+21*x^2-13*x+1): %p A239265 a:= n-> coeff(series(gf, x, n+1), x, n): %p A239265 seq(a(n), n=0..30); %Y A239265 Even bisection of column k=3 of A239264. %K A239265 nonn,easy %O A239265 0,2 %A A239265 _Alois P. Heinz_, Mar 13 2014