A245620 Number of unitary polyominoes with n cells. A unitary polyomino is a polyomino whose edges all have length 1.

1, 0, 0, 0, 1, 0, 0, 1, 1, 0, 2, 2, 3, 4, 7, 10, 17, 28, 47, 69

Offset: 1

Author

George Sicherman, Jul 27 2014

Keywords

• nonn
• hard
• more
• nice

Comments

If a unitary polyomino is colored in checks, all cells on each boundary have the same color. This characterizes unitary polyominoes.

Examples

			The monomino (a single square) is unitary.  The domino, trominoes, and tetrominoes are not.  The X pentomino is unitary; the other pentominoes are not.
		

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

Crossrefs

Cf. A000105 (number of free polyominoes with n cells).

Cf. A245660 (unitary polyominoes without holes).