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A180604
Number of "pieces" of the n-th Brillouin zone of a 2D hexagonal lattice.
1
1, 6, 6, 6, 12, 18, 30, 30, 18, 18, 36, 42, 54, 54, 42, 66
OFFSET
1,2
COMMENTS
Each Brillouin zone has the same area, and they are all equivalent mod the periodicity of the lattice, but the higher-order ones consist of a set of polygons. This is the number of polygons in that set.
EXAMPLE
The 2nd Brillouin zone consists of 6 equilateral triangles, so a(2) = 6. The 5th Brillouin zone consists of 12 30-60-90 triangles, so a(5) = 12.
CROSSREFS
Sequence in context: A315827 A315828 A315829 * A254572 A360561 A109047
KEYWORD
nonn,more
AUTHOR
Keenan Pepper, Sep 11 2010
STATUS
approved