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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 (list; graph; refs; listen; history; text; internal format)
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: A066642 A019988 A137732 * 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

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Last modified October 23 05:13 EDT 2018. Contains 316519 sequences. (Running on oeis4.)