OFFSET
1,4
COMMENTS
This is one of three sequences used to calculate A030223, the number of achiral polyominoes for this tiling. Two fixed polyominoes are identical only if one is a translation of the other.
LINKS
Robert A. Russell, Table of n, a(n) for n = 1..60
FORMULA
EXAMPLE
These are the n-ominoes for n<6. The highest point of the polyomino on the vertical axis of symmetry must be a cell vertex.
________ ________ ________
/\ /\ \ /\ / /\ \ /\ / /\ /\ /\ /\ /\
/__\ /__\ \/__\/ /__\ \/__\/ /__\/__\ /__\/__\/__\
\ / /\ /\ \ / \ /\ /
\/ /__\/__\ \/ \/__\/
CROSSREFS
KEYWORD
nonn
AUTHOR
Robert A. Russell, Jul 26 2023
STATUS
approved