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A056304
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Number of primitive (period n) n-bead necklace structures using exactly three different colored beads.
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5
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0, 0, 1, 2, 5, 17, 43, 124, 338, 941, 2591, 7234, 20125, 56407, 158349, 446492, 1262225, 3580330, 10181479, 29031306, 82968799, 237642659, 682014587, 1960974220, 5647919640, 16292741605, 47069104274, 136166647110, 394418199725, 1143821887473, 3320790074371
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OFFSET
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1,4
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COMMENTS
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Turning over the necklace is not allowed. Colors may be permuted without changing the necklace structure.
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REFERENCES
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M. R. Nester (1999). Mathematical investigations of some plant interaction designs. PhD Thesis. University of Queensland, Brisbane, Australia. [See A056391 for pdf file of Chap. 2]
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LINKS
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FORMULA
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a(n) = Sum_{d|n} mu(d)*A056296(n/d), where mu = A008683 is the Möbius function.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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