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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
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.
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: A361440 A143590 A336030 * A059348 A110871 A243856
KEYWORD
nonn,hard,more,nice
AUTHOR
George Sicherman, Jul 27 2014
STATUS
approved