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A048243
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Number of non-unitary divisors of binomial(n, floor(n/2)).
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4
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0, 0, 0, 0, 0, 2, 0, 0, 4, 10, 0, 8, 8, 16, 8, 16, 0, 16, 0, 16, 32, 64, 0, 32, 80, 128, 224, 320, 256, 352, 64, 128, 256, 512, 256, 640, 640, 1024, 512, 1280, 512, 1024, 512, 1024, 2560, 3328, 1280, 2432, 2432, 3584, 3584, 5120, 2048, 2816, 2048, 4096, 8192
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OFFSET
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1,6
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LINKS
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FORMULA
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EXAMPLE
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At n = 10, binomial(10,5) = 252 = 4*9*7 has 18 divisors, 8 are unitary and the residual 10 are non-unitary; thus a(10) = 10 = 18 - 8.
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MATHEMATICA
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Table[Function[k, DivisorSum[k, 1 &, ! CoprimeQ[#, k/#] &]]@ Binomial[n, Ceiling[n/2]], {n, 57}] (* Michael De Vlieger, Jun 29 2017 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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