OFFSET
0,4
EXAMPLE
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:
._._____. ._____._. ._._._._.
| |_____| |_____| | | . | . |
| | . | | | | . | | |___|___|
|_|___| | | |___|_| | . | . |
|_____|_| |_|_____| |___|___| .
CROSSREFS
KEYWORD
nonn,more
AUTHOR
Alois P. Heinz, Dec 02 2012
EXTENSIONS
a(12) from Alois P. Heinz, Sep 24 2014
STATUS
approved