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A075217
Number of polyiamonds with 2n cells that tile the plane by translation but not by 180-degree rotation (Conway criterion).
10
0, 0, 0, 0, 1, 22, 38, 504, 1468, 6945, 11046, 115186, 119496, 677774, 2013619
OFFSET
1,6
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 Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Section 9.4.
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