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%I #17 May 17 2022 13:22:51
%S 1,0,1,2,3,28,267,2744,66653,2766100,141365332,13305552648,
%T 2149055591278
%N Number of tilings of an n X n square using straight (3 X 1) trominoes and 2 X 2 tiles.
%e a(4) = 3, because there are 3 tilings of a 4 X 4 square using straight (3 X 1) trominoes and 2 X 2 tiles:
%e ._._____. ._____._. ._._._._.
%e | |_____| |_____| | | . | . |
%e | | . | | | | . | | |___|___|
%e |_|___| | | |___|_| | . | . |
%e |_____|_| |_|_____| |___|___| .
%Y Main diagonal of A219967.
%Y Cf. A233807.
%K nonn,more
%O 0,4
%A _Alois P. Heinz_, Dec 02 2012
%E a(12) from _Alois P. Heinz_, Sep 24 2014
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