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A129452
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Expansion of (-1+9*x^2+27*x^3) / ((1+3*x+9*x^2) *(-1+4*x+9*x^2+9*x^3-81*x^4)).
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0
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1, 1, 4, 61, 208, 1093, 7198, 35560, 193450, 1089772, 5837140, 31840051, 174564403, 949080799, 5176371973, 28253599486, 154003756249, 839880083245, 4580937825271, 24980164298164, 136230227328730, 742951002036193
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OFFSET
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0,3
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COMMENTS
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The case q=3 of the formula given in A129443; the term q*x^2 also missing here. The formula in the paper generates 1, 1, 7, 76, 316, 1915, 12298, 68860,.... - R. J. Mathar, Sep 09 2011
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LINKS
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Table of n, a(n) for n=0..21.
Sara Billey, Gregory Warrington, Kazhdan-Lusztig Polynomials for 321-hexagon-avoiding permutations, J. of Algebraic Combinatorics 13 (2) (2001) 111-136, page 132.
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MATHEMATICA
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p[x_, q_] = (-1 + q^2*x^2 + q^3*x^3)/((1 + q*x + q^2*x^2)*(-1 + x + q*x + q^2*x^2 + q^2*x^3 - q^4*x^4)); Table[ SeriesCoefficient[Series[p[x, 3], {x, 0, 30}], n], {n, 0, 30}]
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CROSSREFS
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Sequence in context: A173607 A071582 A158300 * A131014 A118005 A132064
Adjacent sequences: A129449 A129450 A129451 * A129453 A129454 A129455
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KEYWORD
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nonn,less
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AUTHOR
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Roger L. Bagula, Jun 08 2007
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STATUS
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approved
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