Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #8 Dec 07 2012 12:44:43
%S 1,3,60,1562,29907,707903,15859323,354859954,8061851335,181382499259,
%T 4095897476480,92476840837163,2086314577400136,47096964973772265,
%U 1062921614745008697,23989328157229264043,541446343762904191567,12220135872229640539724
%N Number of tilings of a 7 X n rectangle using dominoes and straight (3 X 1) trominoes.
%H Alois P. Heinz, <a href="/A219870/b219870.txt">Table of n, a(n) for n = 0..250</a>
%e a(1) = 3, because there are 3 tilings of a 7 X 1 rectangle using dominoes and straight (3 X 1) trominoes:
%e ._. ._. ._.
%e | | | | | |
%e | | |_| |_|
%e |_| | | | |
%e | | | | |_|
%e |_| |_| | |
%e | | | | | |
%e |_| |_| |_|
%Y Column k=7 of A219866.
%K nonn
%O 0,2
%A _Alois P. Heinz_, Nov 30 2012