OFFSET
1,11
COMMENTS
If a unitary polyomino is colored in checks, all cells on each boundary have the same color. This characterizes unitary polyominoes.
LINKS
Alberto Del Lungo, Massimo Mirolli, Renzo Pinzani, and Simone Rinaldi, A Bijection for Directed Polyominoes, Discrete Mathematics and Theoretical Computer Science Proceedings, AA (2001), 133-144.
George Sicherman, Catalogue of Unitary Polyominoes
EXAMPLE
The monomino (a single square) is unitary. The domino, trominoes, and tetrominoes are not. The X pentomino is unitary; the other pentominoes are not.
CROSSREFS
KEYWORD
nonn,hard,more,nice
AUTHOR
George Sicherman, Jul 27 2014
STATUS
approved