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 A219971 Number of tilings of a 7 X n rectangle using straight (3 X 1) trominoes and 2 X 2 tiles. 2

%I #7 Dec 07 2012 12:52:27

%S 1,0,3,13,31,170,804,2744,12343,55657,214485,923990,4008013,16241904,

%T 68963484,293830787,1216393406,5135225641,21711233759,90692128053,

%U 381960417890,1609647053073,6749229887672,28396742081001,119506154362773,501879008939056

%N Number of tilings of a 7 X n rectangle using straight (3 X 1) trominoes and 2 X 2 tiles.

%H Alois P. Heinz, <a href="/A219971/b219971.txt">Table of n, a(n) for n = 0..500</a>

%e a(2) = 3, because there are 3 tilings of a 7 X 2 rectangle using straight (3 X 1) trominoes and 2 X 2 tiles:

%e ._._. .___. .___.

%e | | | | | | |

%e | | | |___| |___|

%e |_|_| | | | | |

%e | | | | | |___|

%e |___| |_|_| | | |

%e | | | | | | |

%e |___| |___| |_|_|

%Y Column k=7 of A219967.

%K nonn

%O 0,3

%A _Alois P. Heinz_, Dec 02 2012

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