Year-end appeal: Please make a donation to the OEIS Foundation to support ongoing development and maintenance of the OEIS. We are now in our 61st year, we have over 378,000 sequences, and we’ve reached 11,000 citations (which often say “discovered thanks to the OEIS”).
%I #14 Mar 28 2015 22:37:14
%S 1,2,4,48,576,2304,15360,614400,1548288000,3901685760000,
%T 9832248115200000,24777265250304000000,62438708430766080000000,
%U 157345545245530521600000000,5154640062243579887616000000000
%N Denominator of Product_{k=1..n} H(k), where H(k) = Sum_{j=1..k} 1/j, the k-th harmonic number.
%e (1)(1 + 1/2)(1 + 1/2 + 1/3) = 1*(3/2)*(11/6) = 11/4, so a(3) = 4.
%t a[n_] := Denominator[ Product[ HarmonicNumber[k], {k, 1, n}]]; Table[ a[n], {n, 14}] (* _Robert G. Wilson v_, Aug 26 2004 *)
%o (PARI) hh(n)=sum(i=1,n,1/i); ff(n)=denominator(prod(i=1,n,hh(i))); for (i=1,30,print1(ff(i),",")) \\ Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com), Aug 23 2004
%Y Cf. A097423.
%K frac,nonn
%O 1,2
%A _Leroy Quet_, Aug 21 2004
%E More terms from Mohammed Bouayoun (mohammed.bouayoun(AT)sanef.com) and _Robert G. Wilson v_, Aug 23 2004