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A161465
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Number of reduced words of length n in the Weyl group A_13.
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0
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1, 13, 90, 441, 1715, 5629, 16198, 41926, 99412, 218895, 452284, 884170, 1646177, 2934764, 5032235, 8330256, 13354639, 20789572, 31498907, 46541635, 67178356, 94865470, 131234038, 178050835, 237160055, 310405409, 399533919, 506084453
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OFFSET
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0,2
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COMMENTS
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Computed with MAGMA using commands similar to those used to compute A161409.
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REFERENCES
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J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See under Poincaré polynomial.
N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche I.)
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LINKS
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FORMULA
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G.f. for A_m is the polynomial Prod_{k=1..m}(1-x^(k+1))/(1-x). Only finitely many terms are nonzero. This is a row of the triangle in A008302.
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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