%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
