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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 Gr├╝nbaum 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 May 24 22:33 EDT 2015. Contains 257802 sequences.