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%I #22 Dec 14 2017 05:22:57
%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