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A056841 Number of diagonal polyominoes with n cells. 3

%I

%S 1,1,2,5,15,54,212,908,4011,18260

%N Number of diagonal polyominoes with n cells.

%C Apparently the cells are circular blobs which must be connected diagonally and the polyominoes can be rotated by 90 degrees and turned over.

%C Also the number of essentially different (i.e. not related by reflections, translations or rotations) diagrams consisting of n nodes in Z^2 and n-1 horizontal or vertical edges of length 1 between pairs of nodes such that the resulting graph is connected (hence a tree). - _Paul Boddington_, Jul 27 2004

%H R. J. Mathar, <a href="/A056841/a056841.gz">Table of all such polyominoes with n <= 10 cells</a> (gzipped)

%H R. J. Mathar, <a href="/A056841/a056841.cpp.txt">C++ program</a>

%H M. Vicher, <a href="http://www.vicher.cz/puzzle/polyforms.htm">Polyforms</a>

%H M. Vicher, <a href="http://www.vicher.cz/puzzle/polyform/minio/images/d1.gif">The 15 5-celled diagonal polyominoes</a>

%H M. Vicher, <a href="/A056841/a056841.gif">The 15 5-celled diagonal polyominoes</a>

%e The polyominoes with 1, 2, 3 and 4 cells are

%e O..O...O...O.O..O....O....O.....O....O.O

%e ....O...O...O....O....O....O...O.O..O.O.

%e .........O........O....O..O.O...O.......

%e ...................O..O.................

%Y See also A056840, A056787.

%K nonn,nice,more

%O 1,3

%A _James A. Sellers_, Aug 28 2000

%E Description revised by _N. J. A. Sloane_, Jun 21 2001

%E a(10) from _R. J. Mathar_, Apr 10 2006

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Last modified March 26 23:16 EDT 2019. Contains 321566 sequences. (Running on oeis4.)