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 A239266 #12 Nov 23 2018 06:44:21 %S A239266 1,1,11,43,280,1563,9415,55553,331133,1968400,11716601,69716257, %T A239266 414898579,2469046811,14693544104,87442204835,520375602855, %U A239266 3096794588441,18429266069421,109673987617376,652678415082545,3884139865306433,23114817718082715,137558073518189643 %N A239266 Number of domicule tilings of a 4 X n grid. %C A239266 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 A239266 Alois P. Heinz, <a href="/A239266/b239266.txt">Table of n, a(n) for n = 0..1000</a> %F A239266 G.f.: -(x-1)*(x^3-x^2+5*x-1)/(5*x^6-11*x^5+30*x^4-30*x^3-2*x^2+7*x-1). %e A239266 a(2) = 11: %e A239266 +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ %e A239266 |o o| |o o| |o o| |o-o| |o o| |o-o| |o o| |o o| |o-o| |o-o| |o-o| %e A239266 | X | | X | | X | | | || || | | || || || || | | | | | | %e A239266 |o o| |o o| |o o| |o o| |o o| |o-o| |o o| |o o| |o-o| |o-o| |o o| %e A239266 | | | | | | | X | | | | | | | | | | | | | || || %e A239266 |o o| |o o| |o-o| |o o| |o o| |o o| |o o| |o-o| |o o| |o-o| |o o| %e A239266 | X | || || | | | | | X | | X | || || | | || || | | | | %e A239266 |o o| |o o| |o-o| |o-o| |o o| |o o| |o o| |o-o| |o o| |o-o| |o-o| %e A239266 +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+ +---+. %p A239266 gf:= -(x-1)*(x^3-x^2+5*x-1)/(5*x^6-11*x^5+30*x^4-30*x^3-2*x^2+7*x-1): %p A239266 a:= n-> coeff(series(gf, x, n+1), x, n): %p A239266 seq(a(n), n=0..30); %Y A239266 Column k=4 of A239264. %K A239266 nonn,easy %O A239266 0,3 %A A239266 _Alois P. Heinz_, Mar 13 2014