A128598 - OEIS

%I #3 Mar 30 2012 18:37:03

%S 1,24,297,3210,32510,318171,3054100,28980565,273077443,2562036673,

%T 23973009386,223949654108,2090070431683,19496003736658,

%U 181815760387221,1695523268254637,15813185728272754,147508341317700463

%N Column 3 of triangle A128596; a(n) = coefficient of q^(3n+9) in the q-analog of the even double factorials (2n+6)!! for n>=0.

%F a(n) = [q^(3n+9)] Product_{j=1..n+3} (1-q^(2j))/(1-q) for n>=0.

%o (PARI) {a(n)=polcoeff(prod(j=1,n+3,(1-q^(2*j))/(1-q)),3*n+9,q)}

%Y Cf. A128596; A128084; A000165 ((2n)!!); A128086 (column 1), A128597 (column 2).

%K nonn

%O 0,2

%A _Paul D. Hanna_, Mar 12 2007