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A180604
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Number of "pieces" of the n-th Brillouin zone of a 2D hexagonal lattice.
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1
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1, 6, 6, 6, 12, 18, 30, 30, 18, 18, 36, 42, 54, 54, 42, 66
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OFFSET
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1,2
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COMMENTS
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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.
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LINKS
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EXAMPLE
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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.
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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STATUS
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approved
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