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 A219873 #10 Sep 30 2014 16:42:40 %S A219873 1,7,506,58002,4631107,458901955,43427618185,4095897476480, %T A219873 392127322268846,37197513508819191,3541054185616706122, %U A219873 337034306456285944790,32054951461147041813900,3050527403495695959369072,290235791993563362905189432,27614468898770593799634611889 %N A219873 Number of tilings of a 10 X n rectangle using dominoes and straight (3 X 1) trominoes. %H A219873 Alois P. Heinz, <a href="/A219873/b219873.txt">Table of n, a(n) for n = 0..60</a> %e A219873 a(1) = 7, because there are 7 tilings of a 10 X 1 rectangle using dominoes and straight (3 X 1) trominoes: %e A219873 ._. ._. ._. ._. ._. ._. ._. %e A219873 | | | | | | | | | | | | | | %e A219873 |_| |_| |_| |_| | | | | | | %e A219873 | | | | | | | | |_| |_| |_| %e A219873 |_| |_| | | | | | | | | | | %e A219873 | | | | |_| |_| |_| |_| | | %e A219873 |_| | | | | | | | | | | |_| %e A219873 | | |_| |_| | | |_| | | | | %e A219873 |_| | | | | |_| | | |_| |_| %e A219873 | | | | | | | | | | | | | | %e A219873 |_| |_| |_| |_| |_| |_| |_| %Y A219873 Column k=10 of A219866. %K A219873 nonn %O A219873 0,2 %A A219873 _Alois P. Heinz_, Nov 30 2012