OFFSET
0,3
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
Vaclav Kotesovec, Recurrence (of order 126) and G.f.
Wikipedia, Tromino
EXAMPLE
a(2) = 11:
.___. .___. .___. .___. .___. .___. .___. .___. .___. .___. .___.
| | | | ._| |_. | | ._| | | | |_. | | | | |_. | | ._| | ._| |_. |
| | | |_| | | |_| |_| | | | | | |_| | | | | |_| |_| | |_| | | |_|
|_|_| |___| |___| |___| |_|_| |___| |_|_| |___| |___| | | | | | |
| | | | ._| |_. | | | | | ._| | | | |_. | | ._| |_. | | |_| |_| |
| | | |_| | | |_| | | | |_| | | | | | |_| |_| | | |_| |_| | | |_|
|_|_| |___| |___| |_|_| |___| |_|_| |___| |___| |___| |___| |___|.
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Dec 06 2013
STATUS
approved