OFFSET
1,4
COMMENTS
Consider only the corners of the polygon that forms the border of the polyomino. Then build the bracelet of black and white beads by following the border of the polygon in a clockwise direction, adding a black bead for each right-turning right angle, and a white bead for each left-turning right angle. Count in this sequence only polyominoes for which no smaller polyomino has the same bracelet. Note 2 polyominoes of the same size having the same bracelet will count as 2.
EXAMPLE
a(2) is 0 as the domino has bracelet BBBB, which is the same as the monomino.
CROSSREFS
KEYWORD
nonn,more
AUTHOR
John Mason, Allan C. Wechsler, Mar 15 2021
STATUS
approved