OFFSET
1,6
COMMENTS
An X-frame polyomino has a perimeter that forms a self-avoiding polygon such that as you traverse the perimeter counterclockwise you encounter turns in the order LLRLLRLLRLLR.
EXAMPLE
a(5) = 1 because of:
O
OOO
O
The a(7) = 7 polyominoes are:
O O O O O O O
OOOOO OOOOO OOOOO OOOOO OOOO OOOO OOOO
O O O O O O OO
O O
CROSSREFS
KEYWORD
nonn,more
AUTHOR
John Mason, Feb 06 2023
STATUS
approved