%I A090648
%S A090648 0,1,1,3,17,31,3,5461,257,657,6355,60787,12291,22369621,617093,149943,
%T A090648 168,43009,5726623061,71613,91625968981,162529435,4870483401,
%U A090648 50991843607,4990,69107643,12129927891,34118178995231,5664905191661
%N A090648 a(n)=2*(4^n-1)/denominator(B(2n)) where B(k) denotes the k-th Bernoulli 
               number.
%o A090648 (PARI) a(n)=2*(4^n-1)/denominator(bernfrac(2*n))
%Y A090648 Cf. A001469.
%Y A090648 Sequence in context: A107158 A152529 A126782 this_sequence A031024 A045437 
               A115355
%Y A090648 Adjacent sequences: A090645 A090646 A090647 this_sequence A090649 A090650 
               A090651
%K A090648 nonn
%O A090648 0,4
%A A090648 Benoit Cloitre (benoit7848c(AT)orange.fr), Dec 13 2003 Ben