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A189980
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a(n) is the number of incongruent two-color bracelets of n beads, 10 from them are black (A005515), having a diameter of symmetry.
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4
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1, 1, 6, 6, 21, 21, 56, 56, 126, 126, 252, 252, 462, 462, 792, 792, 1287, 1287, 2002, 2002, 3003, 3003, 4368, 4368, 6188, 6188, 8568, 8568, 11628, 11628, 15504, 15504, 20349, 20349, 26334, 26334, 33649, 33649
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OFFSET
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10,3
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COMMENTS
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For n >= 11, a(n-1) is the number of incongruent two-color bracelets of n beads, 11 from them are black (A032282), having a diameter of symmetry.
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LINKS
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Index entries for linear recurrences with constant coefficients, signature (1,5,-5,-10,10,10,-10,-5,5,1,-1).
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FORMULA
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a(n) = binomial(floor(n/2), 5). [Typo fixed by Colin Barker, Feb 07 2013]
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MAPLE
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MATHEMATICA
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Table[Binomial[Floor[n/2], 5], {n, 10, 50}] (* Harvey P. Dale, Oct 06 2017 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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