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A336113
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a(n) is the numerator of Sum_{odd d|n} 1/d.
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1
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1, 1, 4, 1, 6, 4, 8, 1, 13, 6, 12, 4, 14, 8, 8, 1, 18, 13, 20, 6, 32, 12, 24, 4, 31, 14, 40, 8, 30, 8, 32, 1, 16, 18, 48, 13, 38, 20, 56, 6, 42, 32, 44, 12, 26, 24, 48, 4, 57, 31, 24, 14, 54, 40, 72, 8, 80, 30, 60, 8, 62, 32, 104, 1, 84, 16, 68, 18, 32, 48, 72
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OFFSET
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1,3
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LINKS
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FORMULA
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a(n) = (-1)^(n+1) * A098986(n) for n>=1.
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EXAMPLE
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1, 1, 4/3, 1, 6/5, 4/3, 8/7, 1, 13/9, 6/5, 12/11, 4/3, 14/13, 8/7, 8/5, 1, ...
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MATHEMATICA
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a[n_] := Numerator @ DivisorSum[n, 1/# &, OddQ[#] &]; Array[a, 100] (* Amiram Eldar, Jul 09 2020 *)
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PROG
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(PARI) a(n) = numerator(sumdiv(n, d, if (d%2, 1/d)));
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CROSSREFS
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KEYWORD
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nonn,frac
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AUTHOR
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STATUS
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approved
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