|
|
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 Grünbaum and G. C. Shephard, Tilings and Patterns. W. H. Freeman, New York, 1987, Section 9.4.
|
|
LINKS
|
|
|
CROSSREFS
|
Cf. A071332, A075216, A075217, A075219, A075220, A075221, A075222, A075223, A075224, A075200, A075209.
|
|
KEYWORD
|
hard,nonn
|
|
AUTHOR
|
|
|
EXTENSIONS
|
|
|
STATUS
|
approved
|
|
|
|