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A082688 Denominator of Sum_{k=1..n} 1/(n+k). 2
2, 12, 60, 840, 2520, 27720, 360360, 144144, 2450448, 232792560, 232792560, 5354228880, 26771144400, 11473347600, 332727080400, 20629078984800, 20629078984800, 144403552893600, 5342931457063200, 5342931457063200 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

T. D. Noe, Table of n, a(n) for n=1..100

FORMULA

limit n ->infinity Sum_{k=1..n} 1/(n+k) = log(2).

Denominator of Psi(2*n+1)-Psi(n+1). - Vladeta Jovovic, Aug 24 2003

EXAMPLE

1/2, 7/12, 37/60, 533/840, 1627/2520, 18107/27720, 237371/360360, ...

MATHEMATICA

Table[HarmonicNumber[2 n] - HarmonicNumber[n], {n, 20}] // Denominator (* Eric W. Weisstein, Dec 14 2017 *)

PROG

(PARI) a(n) = denominator(sum(k=1, n, 1/(n+k))); \\ Michel Marcus, Dec 14 2017

CROSSREFS

Cf. A058312, A082687 (numerators).

Sequence in context: A061834 A190425 A145630 * A099996 A099795 A127044

Adjacent sequences:  A082685 A082686 A082687 * A082689 A082690 A082691

KEYWORD

frac,nonn,easy

AUTHOR

Benoit Cloitre, Apr 12 2003

STATUS

approved

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Last modified March 23 13:35 EDT 2019. Contains 321430 sequences. (Running on oeis4.)