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 #18 Feb 15 2021 15:43:42
%S 1,2,3,3,30,30,35,35,210,210,1155,1155,10010,10010,15015,15015,510510,
%T 510510,1616615,1616615,1939938,1939938,22309287,22309287,74364290,
%U 74364290,111546435,111546435,6469693230,6469693230,33426748355,33426748355,200560490130,200560490130
%N Denominator of 1 - Sum_{i=1..n} Bernoulli(i).
%H Amiram Eldar, <a href="/A100650/b100650.txt">Table of n, a(n) for n = 0..2369</a>
%e 1, 3/2, 4/3, 4/3, 41/30, 41/30, 47/35, 47/35, 289/210, 289/210, 1502/1155, 1502/1155, 15551/10010, 15551/10010, 5809/15015, 5809/15015, 3818123/510510, 3818123/510510, ... = A100649/A100650.
%p A100650 := proc(n) 1-add( bernoulli(i),i=1..n) ; denom(%) ; end proc: # _R. J. Mathar_, Jul 01 2011
%t Denominator[1-Accumulate[BernoulliB[Range[0,40]]]] (* _Harvey P. Dale_, Feb 19 2015 *)
%o (PARI) a(n) = denominator(1 - sum(i=1, n, bernfrac(i))); \\ _Michel Marcus_, Feb 15 2021
%Y Cf. A002110
%K nonn,frac
%O 0,2
%A _N. J. A. Sloane_, Dec 05 2004