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A161521
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Number of reduced words of length n in the Weyl group A_22.
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0
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1, 22, 252, 2001, 12374, 63481, 281083, 1103587, 3917728, 12761596, 38582270, 109256095, 291946589, 740676682, 1793325939, 4161927624, 9293159292, 20029728894, 41788665040, 84604366100, 166583279325, 319610939055
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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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