%I A157004
%S A157004 1,2,6,18,58,192,650,2232,7746,27096,95376,337404,1198546,4272308,
%T A157004 15273888,54744268,196646922,707747988,2551624304,9213416524,
%U A157004 33313656888,120604436624,437112790668,1585877246424,5759085911154
%N A157004 Transform of central binomial coefficients A000984 whose Hankel transform 
               obeys a Somos-4 recurrence.
%C A157004 Hankel transform is A157005. Image of A000984 under Riordan array (1,
               x(1-x^2)).
%F A157004 G.f.: 1/sqrt(1-4x(1-x^2));
%F A157004 a(n)=sum{k=0..n, (-1)^((n-k)/2)*(1+(-1)^(n-k))*C(k,floor((n-k)/2))*A000984(k)/
               2}.
%Y A157004 Cf. A157003.
%Y A157004 Sequence in context: A081057 A000137 A151282 this_sequence A085139 A150041 
               A150042
%Y A157004 Adjacent sequences: A157001 A157002 A157003 this_sequence A157005 A157006 
               A157007
%K A157004 easy,nonn
%O A157004 0,2
%A A157004 Paul Barry (pbarry(AT)wit.ie), Feb 20 2009