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A075218 Number of polyiamonds with 2n cells that tile the plane both by translation and by 180-degree rotation (Conway criterion). 10
1, 2, 8, 24, 61, 269, 501, 2121, 4709, 14978, 26675, 123081, 179707, 660366, 1479114 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Polyiamonds with an odd number of cells have different numbers of triangles with the two orientations and so cannot tile by translation.

REFERENCES

Branko Gruenbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Section 9.4.

LINKS

Table of n, a(n) for n=1..15.

Joseph Myers, Polyiamond tiling

CROSSREFS

Cf. A071332, A075216, A075217, A075219, A075220, A075221, A075222, A075223, A075224, A075200, A075209.

Sequence in context: A051745 A006734 A131064 * A006728 A234933 A222808

Adjacent sequences:  A075215 A075216 A075217 * A075219 A075220 A075221

KEYWORD

hard,nonn

AUTHOR

Joseph Myers, Sep 08 2002

EXTENSIONS

More terms from Joseph Myers, Nov 11 2003

a(15) (30-iamonds) from Joseph Myers, Nov 21 2010

STATUS

approved

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Last modified October 22 04:03 EDT 2014. Contains 248388 sequences.