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Search: id:A161717
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| A161717 |
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Number of reduced words of length n in the Weyl group B_8. |
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+0
1
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| 1, 8, 35, 112, 293, 664, 1350, 2520, 4389, 7216, 11298, 16960, 24541, 34376, 46775, 62000, 80241, 101592, 126029, 153392, 183373, 215512, 249202, 283704, 318171, 351680, 383270, 411984, 436913, 457240, 472281, 481520, 484636, 481520, 472281
(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 II.)
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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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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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