%I A117376
%S A117376 1,3,13,55,240,1057,4688,20879,93250,417272,1869725,8386137,37640961,
%T A117376 169042436,759470361,3413223919,15343588991,68988110756,310233741889,
%U A117376 1395268187372,6275807975664,28230370862051,126996552221811
%N A117376 Expansion of 1/((1-3x*c(x))(1-x^2*c(x))), c(x) the g.f. of A000108.
%C A117376 Diagonal sums of number triangle A117375.
%F A117376 a(n)=sum{k=0..floor(n/2), [k<=n-k]*sum{j=0..n-k, (j/(n-k-j))*C(2n-k-j,
               n-k-j)[k<=j]*3^(j-k)}}
%Y A117376 Sequence in context: A037583 A093834 A033887 this_sequence A151318 A151212 
               A151213
%Y A117376 Adjacent sequences: A117373 A117374 A117375 this_sequence A117377 A117378 
               A117379
%K A117376 easy,nonn
%O A117376 0,2
%A A117376 Paul Barry (pbarry(AT)wit.ie), Mar 10 2006