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A058312
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Denominator of the n-th alternating harmonic number, sum ((-1)^(k+1)/k, k=1..n).
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23
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1, 2, 6, 12, 60, 60, 420, 840, 2520, 2520, 27720, 27720, 360360, 360360, 72072, 144144, 2450448, 2450448, 46558512, 232792560, 232792560, 232792560, 5354228880, 5354228880, 26771144400, 26771144400, 80313433200, 11473347600
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history;
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internal format)
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OFFSET
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1,2
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LINKS
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T. D. Noe, Table of n, a(n) for n=1..200
Eric Weisstein's World of Mathematics, Harmonic Number
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FORMULA
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G.f. for A058313(n)/ A058312(n) : log(1+x)/(1-x) - Benoit Cloitre, Jun 15 2003
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EXAMPLE
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1, 1/2, 5/6, 7/12, 47/60, 37/60, 319/420, 533/840, 1879/2520, ...
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MAPLE
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A058313 := n->denom(add((-1)^(k+1)/k, k=1..n));
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PROG
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(PARI) a(n)=denominator(polcoeff(-log(1-x)/(x+1)+O(x^(n+1)), n))
(Haskell)
import Data.Ratio((%), denominator)
a058312 n = a058312_list !! (n-1)
a058312_list = map denominator $ scanl1 (+) $
map (1 %) $ tail a181983_list
-- Reinhard Zumkeller, Mar 20 2013
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CROSSREFS
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Numerators are A058313. Cf. A025530.
Cf. A002805 (denominator of n-th harmonic number).
Cf. A181983.
Sequence in context: A225628 A085911 A211418 * A003418 A109935 A065887
Adjacent sequences: A058309 A058310 A058311 * A058313 A058314 A058315
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KEYWORD
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nonn,frac,nice,easy
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AUTHOR
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N. J. A. Sloane, Dec 09 2000
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STATUS
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approved
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