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%I #25 Apr 26 2023 07:00:08
%S 1,0,0,0,1,0,0,1,1,0,2,2,3,4,7,10,17,28,47,69
%N Number of unitary polyominoes with n cells. A unitary polyomino is a polyomino whose edges all have length 1.
%C If a unitary polyomino is colored in checks, all cells on each boundary have the same color. This characterizes unitary polyominoes.
%H Alberto Del Lungo, Massimo Mirolli, Renzo Pinzani, and Simone Rinaldi, <a href="https://doi.org/10.46298/dmtcs.2298">A Bijection for Directed Polyominoes</a>, Discrete Mathematics and Theoretical Computer Science Proceedings, AA (2001), 133-144.
%H George Sicherman, <a href="https://sicherman.net/nunitary/nunitary.html">Catalogue of Unitary Polyominoes</a>
%e The monomino (a single square) is unitary. The domino, trominoes, and tetrominoes are not. The X pentomino is unitary; the other pentominoes are not.
%Y Cf. A000105 (number of free polyominoes with n cells).
%Y Cf. A245660 (unitary polyominoes without holes).
%K nonn,hard,more,nice
%O 1,11
%A _George Sicherman_, Jul 27 2014