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%I #18 Nov 18 2018 15:41:42
%S 1,0,1,0,6,0,545,5504,652036,44013568,11112714624,3517475475328,
%T 2781543486427548,3568483481372543360,9829161878198755474915,
%U 48599777948701165162242560,484370819140388708451108625276,9036085159101926537420075859958528
%N Number of tilings of an n X n square using right trominoes and 2 X 2 tiles.
%e a(4) = 6, because there are 6 tilings of a 4 X 4 square using right trominoes and 2 X 2 tiles:
%e .___.___. .___.___. .___.___. .___.___. .___.___. .___.___.
%e | . | . | | ._|_. | | ._| . | | ._|_. | | ._|_. | | . |_. |
%e |___|___| |_| . |_| |_| |___| |_| ._|_| |_|_. |_| |___| |_|
%e | . | . | | |___| | | |___| | | |_| . | | . |_| | | |___| |
%e |___|___| |___|___| |___|___| |___|___| |___|___| |___|___|
%Y Main diagonal of A219946.
%Y Cf. A233807.
%K nonn
%O 0,5
%A _Alois P. Heinz_, Dec 01 2012
%E a(15)-a(16) from _Alois P. Heinz_, Sep 24 2014
%E a(17) from _Alois P. Heinz_, Nov 18 2018
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