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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 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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