%I A124131
%S A124131 0,1,1,9,77,1037,19113,464785,14410309,554826453,25971640865,
%T A124131 1452575521241,95664836241981,7327813077384349,645942544224008857,
%U A124131 64924081840553650977,7380723366892082000693,942257770864409337556325
%N A124131 a(n)=((-1)^n/2)*sum_{i1+i2+i3=2n} ((2*n)!/(i1! i2! i3!))*B(i1+i2) where 
               B are the Bernoulli numbers.
%F A124131 a(n) =(-1)^(n+1)*(B(2n)*(4^n-1)-1/2)
%o A124131 (PARI) a(n)=(-1)^(n+1)*(bernfrac(2*n)*(4^n-1)-1/2)
%Y A124131 Cf. A001469.
%Y A124131 Sequence in context: A075608 A126631 A046150 this_sequence A000445 A046196 
               A123918
%Y A124131 Adjacent sequences: A124128 A124129 A124130 this_sequence A124132 A124133 
               A124134
%K A124131 nonn
%O A124131 1,4
%A A124131 Benoit Cloitre (benoit7848c(AT)orange.fr), Nov 30 2006