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 A129452 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)). 0
 1, 1, 4, 61, 208, 1093, 7198, 35560, 193450, 1089772, 5837140, 31840051, 174564403, 949080799, 5176371973, 28253599486, 154003756249, 839880083245, 4580937825271, 24980164298164, 136230227328730, 742951002036193 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 COMMENTS 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 LINKS Sara Billey, Gregory Warrington, Kazhdan-Lusztig Polynomials for 321-hexagon-avoiding permutations, J. of Algebraic Combinatorics 13 (2) (2001) 111-136, page 132. MATHEMATICA 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}] CROSSREFS Sequence in context: A173607 A071582 A158300 * A131014 A118005 A132064 Adjacent sequences:  A129449 A129450 A129451 * A129453 A129454 A129455 KEYWORD nonn,less AUTHOR Roger L. Bagula, Jun 08 2007 STATUS approved

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