

A057973


Number of polybricks: number of ways to arrange n 1 X 2 "bricks" in a wall (see illustrations).


10



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

1,2


COMMENTS

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.


REFERENCES

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]


LINKS

Table of n, a(n) for n=1..20.
Brendan Owen and Livio Zucca, Polyform generation
Brendan Owen and Livio Zucca, The 16 polybricks of order 4
N. J. A. Sloane, The polybricks of orders 1, 2 and 3


CROSSREFS

Sequence in context: A019988 A137732 A119611 * A102461 A176332 A191241
Adjacent sequences: A057970 A057971 A057972 * A057974 A057975 A057976


KEYWORD

nonn,nice


AUTHOR

Warren Power (wjpnply(AT)hotmail.com), Oct 21 2000


EXTENSIONS

More terms from Don Reble, Nov 01 2001
Corrected and extended by Joseph Myers, Sep 21 2002


STATUS

approved



