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Search: id:A161668
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| A161668 |
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Number of reduced words of length n in the Weyl group A_43. |
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+0
1
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| 1, 43, 945, 14146, 162195, 1518760, 12093191, 84189271, 522910058, 2942607305, 15184988654, 72558839841, 323609385853, 1356110885092, 5369781181160, 20188204577529, 72364939854816, 248214470691451, 817302378367149
(list; graph; listen)
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OFFSET
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0,2
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COMMENT
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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 Poincare polynomial.
N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche I.)
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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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KEYWORD
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nonn,new
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AUTHOR
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John Cannon (john(AT)maths.usyd.edu.au) and N. J. A. Sloane (njas(AT)research.att.com), Nov 30 2009
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