%I
%S 1,1,2,7,24,86,315,1170,4389,16588,63064,240901,923858,3554747,
%T 13716315,53054703,205651975,798645126,3106669575,12102626404,
%U 47210910670,184385864445,720920510115,2821499709615,11052719207369,43333403693711
%N A diagonal of the triangle A128084 of coefficients of q in the qanalog of the even double factorials: a(n) = A128084(n,n).
%C See A128082 for a diagonal of the triangle A128080 of coefficients of q in the qanalog of the odd double factorials.
%e a(n) is the nth term in the qanalog of even double factorial (2n)!!, in which the coefficients of q (triangle A128084) begin:
%e (1);
%e 1,(1);
%e 1,2,(2),2,1;
%e 1,3,5,(7),8,8,7,5,3,1;
%e 1,4,9,16,(24),32,39,44,46,44,39,32,24,16,9,4,1;
%e 1,5,14,30,54,(86),125,169,215,259,297,325,340,340,325,297,...;
%e The terms enclosed in parenthesis are initial terms of this sequence.
%o (PARI) a(n)=if(n==0,1,polcoeff(prod(k=1,n,(1q^(2*k))/(1q)),n,q))
%Y Cf. A000165 ((2n)!!); A128084 (triangle), A128085 (central terms).
%K nonn
%O 0,3
%A _Paul D. Hanna_, Feb 14 2007
