OFFSET
1,6
COMMENTS
In other words, free unholey polyominoes with 180-degree rotational symmetry and no other. - John Mason, Oct 11 2022
LINKS
Tomás Oliveira e Silva, Enumeration of polyominoes
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Sep 03 2000
EXTENSIONS
a(29)-a(40) from John Mason, Oct 11 2022
STATUS
approved