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A195506
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Denominators of Sum_{k=1..n} H(k)/k^2; H(k) the k-th harmonic number.
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2
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1, 8, 216, 1728, 216000, 216000, 74088000, 592704000, 16003008000, 16003008000, 21300003648000, 21300003648000, 46796108014656000, 46796108014656000, 46796108014656000, 374368864117248000, 1839274229408039424000, 1839274229408039424000
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OFFSET
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1,2
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COMMENTS
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For the numerators see A195505.
lim n--> infinity (A195505(n)/A195506(n)) = 2*Zeta(3) [L. Euler].
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REFERENCES
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L. Euler, Meditationes circa singulare serierum genus, Novi. Comm. Acad. Sci. Petropolitanae, 20 (1775), 140-186.
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LINKS
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Table of n, a(n) for n=1..18.
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EXAMPLE
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a(2)=8 because 1 + (1+1/2)/2^2 = 11/8.
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MATHEMATICA
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s = 0; Table[s = s + HarmonicNumber[n]/n^2; Denominator[s], {n, 20}] (* T. D. Noe, Sep 20 2011 *)
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CROSSREFS
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Cf. A195505, A002117.
Sequence in context: A163289 A060459 A007409 * A069045 A123057 A009072
Adjacent sequences: A195503 A195504 A195505 * A195507 A195508 A195509
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KEYWORD
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nonn,frac,easy
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AUTHOR
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Franz Vrabec, Sep 19 2011
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STATUS
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approved
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