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A161859
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Number of reduced words of length n in the Weyl group B_13.
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0
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1, 13, 90, 442, 1728, 5720, 16653, 43745, 105586, 237354, 502113, 1007773, 1931631, 3554747, 6308719, 10837683, 18078554, 29362618, 46541560, 72140848, 109543070, 163203326, 238898101, 344008185, 487835165, 681949801, 940569228, 1280958420
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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 II.)
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LINKS
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FORMULA
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G.f. for B_m is the polynomial Prod_{k=1..m}(1-x^(2k))/(1-x). Only finitely many terms are nonzero. This is a row of the triangle in A128084.
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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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