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A219973 Number of tilings of a 9 X n rectangle using straight (3 X 1) trominoes and 2 X 2 tiles.

%I A219973 #7 Dec 07 2012 12:51:34
%S A219973 1,1,5,35,165,1177,9407,55657,372429,2766100,17671945,118674685,
%T A219973 837152398,5531816082,37328192350,257252634864,1725117502706,
%U A219973 11666552132346,79612474584518,537157628862720,3636277021289585,24711657036469040,167150255133278869
%N A219973 Number of tilings of a 9 X n rectangle using straight (3 X 1) trominoes and 2 X 2 tiles.
%H A219973 Alois P. Heinz, <a href="/A219973/b219973.txt">Table of n, a(n) for n = 0..50</a>
%e A219973 a(2) = 5, because there are 5 tilings of a 9 X 2 rectangle using straight (3 X 1) trominoes and 2 X 2 tiles:
%e A219973 .___.   .___.   .___.   .___.   .___.
%e A219973 | | |   | | |   |   |   |   |   |   |
%e A219973 | | |   | | |   |___|   |___|   |___|
%e A219973 |_|_|   |_|_|   | | |   |   |   |   |
%e A219973 | | |   |   |   | | |   |___|   |___|
%e A219973 | | |   |___|   |_|_|   | | |   |   |
%e A219973 |_|_|   |   |   |   |   | | |   |___|
%e A219973 | | |   |___|   |___|   |_|_|   | | |
%e A219973 | | |   |   |   |   |   |   |   | | |
%e A219973 |_|_|   |___|   |___|   |___|   |_|_|
%Y A219973 Column k=9 of A219967.
%K A219973 nonn
%O A219973 0,3
%A A219973 _Alois P. Heinz_, Dec 02 2012