OFFSET
0,3
EXAMPLE
a(2) = 7, because there are 7 tilings of a 10 X 2 rectangle using straight (3 X 1) trominoes and 2 X 2 tiles:
.___. .___. .___. .___. .___. .___. .___.
| | | | | | | | | | | | | | | | |
|___| |___| |___| | | | |___| | | | | | |
| | | | | | | |_|_| | | | |_|_| |_|_|
|___| |___| | | | | | | | | | | | | |
| | | | | |_|_| |___| |_|_| |___| | | |
|___| | | | | | | | | | | | | | |_|_|
| | |_|_| |___| |___| | | | | | | | |
|___| | | | | | | | | | |_|_| |_|_| |___|
| | | | | | | | | | | | | | | | |
|___| |_|_| |_|_| |_|_| |___| |___| |___|
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Dec 02 2012
STATUS
approved