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A057973
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Number of polybricks: number of ways to arrange n 1 X 2 "bricks" in a wall (see illustrations).
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10
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1, 2, 5, 16, 55, 225, 949, 4269, 19500, 91115, 429742, 2047660, 9820197, 47383255, 229725560, 1118568692, 5466616025, 26804560282, 131817042605, 649952289243
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OFFSET
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1,2
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COMMENTS
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The tiling of bricks is topologically the same as that by regular hexagons and this sequence can also be seen as counting polyhexes where two polyhexes are equivalent iff they are related by a symmetry that is also a symmetry of the tiling by bricks.
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REFERENCES
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Other references on polyforms are: www.mathpuzzle.com, Solomon W. Golomb, Ed Pegg, Eric Weisstein, David A. Klarner (Packing rectangles) and Michael Reid [These references should be expanded! - N. J. A. Sloane]
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LINKS
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CROSSREFS
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KEYWORD
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nonn,nice
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AUTHOR
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Warren Power (wjpnply(AT)hotmail.com), Oct 21 2000
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EXTENSIONS
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STATUS
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approved
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