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A245620 Number of unitary polyominoes with n cells.  A unitary polyomino is a polyomino whose edges all have length 1. 1
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), 133-144 (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: A003179 A153934 A143590 * A059348 A110871 A243856

Adjacent sequences:  A245617 A245618 A245619 * A245621 A245622 A245623

KEYWORD

nonn,hard,more,nice

AUTHOR

George Sicherman, Jul 27 2014

STATUS

approved

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Last modified July 25 23:20 EDT 2016. Contains 275038 sequences.