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%I #3 Mar 30 2012 18:37:03
%S 1,7,46,297,1919,12399,80241,520399,3382588,22034519,143826980,
%T 940569228,6161492611,40426009162,265617089899,1747501590554,
%U 11510584144337,75901841055650,501007227527884,3310076954166501
%N Column 2 of triangle A128596; a(n) = coefficient of q^(2n+4) in the q-analog of the even double factorials (2n+4)!! for n>=0.
%F a(n) = [q^(2n+4)] Product_{j=1..n+2} (1-q^(2j))/(1-q) for n>=0.
%o (PARI) {a(n)=polcoeff(prod(j=1,n+2,(1-q^(2*j))/(1-q)),2*n+4,q)}
%Y Cf. A128596; A128084; A000165 ((2n)!!); A128086 (column 1), A128598 (column 3).
%K nonn
%O 0,2
%A _Paul D. Hanna_, Mar 12 2007
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