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A119787
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Numerator of the product of n and the n-th alternating harmonic number, Sum_{k=1..n} (-1)^(k+1)/k.
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6
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1, 1, 5, 7, 47, 37, 319, 533, 1879, 1627, 20417, 18107, 263111, 237371, 261395, 95549, 1768477, 1632341, 33464927, 155685007, 166770367, 156188887, 3825136961, 3602044091, 19081066231, 18051406831, 57128792093, 54260455193
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OFFSET
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1,3
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COMMENTS
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a(n) almost always equals A058313(n), which is the numerator of the n-th alternating harmonic number, Sum ((-1)^(k+1)/k, k=1..n), except for n = 15, 28, 75, 77, 104, ... The ratio a(n)/A058313(n) for n = 1..400 is given in A119788.
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LINKS
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FORMULA
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a(n) = numerator(Sum_{k=1..n} (-1)^(k+1)*n/k).
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EXAMPLE
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The first few fractions are 1, 1, 5/2, 7/3, 47/12, 37/10, 319/60, 533/105, 1879/280, ... = A119787/A334721. - Petros Hadjicostas, May 08 2020
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MATHEMATICA
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Numerator[Table[Sum[(-1)^(i+1)*n/i, {i, 1, n}], {n, 1, 50}]]
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PROG
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(PARI) a(n) = numerator(n*sum(k=1, n, (-1)^(k+1)/k)); \\ Michel Marcus, May 09 2020
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CROSSREFS
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KEYWORD
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frac,nonn
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AUTHOR
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STATUS
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approved
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