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 A219949 #12 Aug 21 2024 10:02:38 %S A219949 1,0,13,16,245,1128,10534,71248,652036,5141408,45081311,377481816, %T A219949 3256166909,27751269104,238314397799,2040642918208,17506339185192, %U A219949 150079258587200,1287249575901534,11038702753296720,94675989650833007,811957493293460552,6963826351562090734 %N A219949 Number of tilings of an 8 X n rectangle using right trominoes and 2 X 2 tiles. %H A219949 Alois P. Heinz, <a href="/A219949/b219949.txt">Table of n, a(n) for n = 0..300</a> %H A219949 <a href="/index/Rec#order_111">Index entries for linear recurrences with constant coefficients</a>, order 111. %e A219949 a(2) = 13, because there are 13 tilings of an 8 X 2 rectangle using right trominoes and 2 X 2 tiles: %e A219949 .___. .___. .___. .___. .___. .___. %e A219949 | ._| | ._| |_. | |_. | | ._| | ._| %e A219949 |_| | |_| | | |_| | |_| |_| | |_| | %e A219949 |___| |___| |___| |___| |___| |___| %e A219949 | ._| |_. | | ._| |_. | | . | | . | %e A219949 |_| | | |_| |_| | | |_| |___| |___| %e A219949 |___| |___| |___| |___| | ._| |_. | %e A219949 | . | | . | | . | | . | |_| | | |_| %e A219949 |___| |___| |___| |___| |___| |___| %e A219949 .___. .___. .___. .___. .___. .___. .___. %e A219949 |_. | |_. | | . | | . | | . | | . | | . | %e A219949 | |_| | |_| |___| |___| |___| |___| |___| %e A219949 |___| |___| | ._| | ._| |_. | |_. | | . | %e A219949 | . | | . | |_| | |_| | | |_| | |_| |___| %e A219949 |___| |___| |___| |___| |___| |___| | . | %e A219949 | ._| |_. | | ._| |_. | | ._| |_. | |___| %e A219949 |_| | | |_| |_| | | |_| |_| | | |_| | . | %e A219949 |___| |___| |___| |___| |___| |___| |___| %Y A219949 Column k=8 of A219946. %K A219949 nonn %O A219949 0,3 %A A219949 _Alois P. Heinz_, Dec 01 2012