%I A138240
%S A138240 0,1,6,40,296,2400,20928,192768,1848960,18277888,184890368,1904259072,
%T A138240 19898765312,210424545280,2247494172672,24209586782208,262696649785344,
%U A138240 2868744309571584,31504024885002240,347697247933169664
%N A138240 Expansion of (1/4)(1-sqrt(1-12x)/sqrt(1-4x)).
%C A138240 Hankel transform of a(n) is -4^comb(n,2)*A099156(n)=-4^comb(n,2)*[x^n](x/
               (1-8x+4x^2)).
%C A138240 Hankel transform of a(n+1) is 4^comb(n+1,2)=A053763(n+1).
%C A138240 Hankel transform of a(n+2) is 4^comb(n+1,2)*A102591(n+1)=4^comb(n+1,2)*[x^n](6-4x)/
               (1-8x+4x^2).
%Y A138240 Cf. A104498.
%Y A138240 Sequence in context: A069720 A005037 A081337 this_sequence A083805 A006387 
               A014481
%Y A138240 Adjacent sequences: A138237 A138238 A138239 this_sequence A138241 A138242 
               A138243
%K A138240 easy,nonn
%O A138240 0,3
%A A138240 Paul Barry (pbarry(AT)wit.ie), Mar 07 2008