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A128598
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.
2
1, 24, 297, 3210, 32510, 318171, 3054100, 28980565, 273077443, 2562036673, 23973009386, 223949654108, 2090070431683, 19496003736658, 181815760387221, 1695523268254637, 15813185728272754, 147508341317700463
OFFSET
0,2
FORMULA
a(n) = [q^(3n+9)] Product_{j=1..n+3} (1-q^(2j))/(1-q) for n>=0.
PROG
(PARI) {a(n)=polcoeff(prod(j=1, n+3, (1-q^(2*j))/(1-q)), 3*n+9, q)}
CROSSREFS
Cf. A128596; A128084; A000165 ((2n)!!); A128086 (column 1), A128597 (column 2).
Sequence in context: A187028 A186966 A281134 * A161524 A161931 A162366
KEYWORD
nonn
AUTHOR
Paul D. Hanna, Mar 12 2007
STATUS
approved