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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

%I

%S 1,1,4,61,208,1093,7198,35560,193450,1089772,5837140,31840051,

%T 174564403,949080799,5176371973,28253599486,154003756249,839880083245,

%U 4580937825271,24980164298164,136230227328730,742951002036193

%N 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)).

%C 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

%H Sara Billey, Gregory Warrington, <a href="http://dx.doi.org/10.1023/A:1011279130416">Kazhdan-Lusztig Polynomials for 321-hexagon-avoiding permutations</a>, J. of Algebraic Combinatorics 13 (2) (2001) 111-136, page 132.

%t 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}]

%K nonn,less

%O 0,3

%A _Roger L. Bagula_, Jun 08 2007

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Last modified September 24 03:26 EDT 2021. Contains 347623 sequences. (Running on oeis4.)