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A128593 Column 1 of triangle A128592; a(n) = coefficient of q^(n+2) in the q-analog of the odd double factorials (2n+3)!! for n>=0. 3
1, 3, 12, 45, 170, 644, 2451, 9365, 35908, 138104, 532589, 2058782, 7975216, 30951921, 120326060, 468473348, 1826415556, 7129330988, 27860219331, 108984557708, 426730087879, 1672310507262, 6558840830680, 25742937514814 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..23.

FORMULA

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

PROG

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

CROSSREFS

Cf. A128592; A128080; A001147 ((2n-1)!!); A128594 (column 2), A128595 (row sums).

Sequence in context: A064017 A005320 A062561 * A085481 A030195 A114515

Adjacent sequences:  A128590 A128591 A128592 * A128594 A128595 A128596

KEYWORD

nonn

AUTHOR

Paul D. Hanna, Mar 12 2007

STATUS

approved

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Last modified December 11 00:29 EST 2016. Contains 279033 sequences.