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 A082688 Denominator of Sum_{k=1..n} 1/(n+k). 2

%I

%S 2,12,60,840,2520,27720,360360,144144,2450448,232792560,232792560,

%T 5354228880,26771144400,11473347600,332727080400,20629078984800,

%U 20629078984800,144403552893600,5342931457063200,5342931457063200

%N Denominator of Sum_{k=1..n} 1/(n+k).

%H T. D. Noe, <a href="/A082688/b082688.txt">Table of n, a(n) for n=1..100</a>

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

%F Denominator of Psi(2*n+1)-Psi(n+1). - _Vladeta Jovovic_, Aug 24 2003

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

%t Table[HarmonicNumber[2 n] - HarmonicNumber[n], {n, 20}] // Denominator (* _Eric W. Weisstein_, Dec 14 2017 *)

%o (PARI) a(n) = denominator(sum(k=1, n, 1/(n+k))); \\ _Michel Marcus_, Dec 14 2017

%Y Cf. A058312, A082687 (numerators).

%K frac,nonn,easy

%O 1,1

%A _Benoit Cloitre_, Apr 12 2003

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Last modified April 20 03:03 EDT 2019. Contains 322294 sequences. (Running on oeis4.)