

A245620


Number of unitary polyominoes with n cells. A unitary polyomino is a polyomino whose edges all have length 1.


2



1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 2, 2, 3, 4, 7, 10, 17, 28, 47, 69
(list;
graph;
refs;
listen;
history;
text;
internal format)



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

Table of n, a(n) for n=1..20.
Alberto Del Lungo, Massimo Mirolli, Renzo Pinzani, and Simone Rinaldi, "A Bijection for Directed Polyominoes," Discrete Mathematics and Theoretical Computer Science Proceedings, AA (2001), 133144 (PDF
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

Cf. A000105, number of free polyominoes with n cells.
Cf. A245660, unitary polyominoes without holes.
Sequence in context: A153934 A143590 A336030 * A059348 A110871 A243856
Adjacent sequences: A245617 A245618 A245619 * A245621 A245622 A245623


KEYWORD

nonn,hard,more,nice


AUTHOR

George Sicherman, Jul 27 2014


STATUS

approved



