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A128598
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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.
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2
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1, 24, 297, 3210, 32510, 318171, 3054100, 28980565, 273077443, 2562036673, 23973009386, 223949654108, 2090070431683, 19496003736658, 181815760387221, 1695523268254637, 15813185728272754, 147508341317700463
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = [q^(3n+9)] Product_{j=1..n+3} (1-q^(2j))/(1-q) for n>=0.
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PROG
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(PARI) {a(n)=polcoeff(prod(j=1, n+3, (1-q^(2*j))/(1-q)), 3*n+9, q)}
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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