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Search: id:A128595
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| 1, 2, 5, 26, 189, 1734, 19305, 253370, 3828825, 65473006, 1249937325, 26352843470, 608142583125, 15247003381854, 412685556908625, 11993673995924378, 372509404162520625, 12313505304343363126, 431620764875678503125
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OFFSET
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0,2
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COMMENT
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A128592(n,k) is the coefficient of q^(nk+k) in the q-analog of the odd double factorials (2n-1)!!.
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FORMULA
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a(n) = Sum_{k=0..n} { [q^(nk+k)] Product_{j=1..n+1} (1-q^(2j-1))/(1-q) } for n>=0.
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PROGRAM
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(PARI) {a(n)=sum(k=0, n, polcoeff(prod(j=1, n+1, (1-q^(2*j-1))/(1-q)), (n+1)*k, q))}
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CROSSREFS
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Cf. A128592; A128080; A001147 ((2n-1)!!); A128593 (column 1), A128594 (column 2).
Sequence in context: A120762 A072268 A019014 this_sequence A111195 A064006 A003095
Adjacent sequences: A128592 A128593 A128594 this_sequence A128596 A128597 A128598
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KEYWORD
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nonn
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AUTHOR
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Paul D. Hanna (pauldhanna(AT)juno.com), Mar 12 2007
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