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A162183
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Number of reduced words of length n in the Weyl group B_45.
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0
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1, 45, 1034, 16170, 193544, 1890624, 15695085, 113852001, 736452870, 4313931566, 23162284321, 115106177245, 533700057015, 2324210876515, 9560626910011, 37327619195919, 138907067703060, 494486307393900, 1689330735102480
(list; graph; refs; listen; history; internal format)
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OFFSET
| 0,2
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COMMENTS
| Computed with MAGMA using commands similar to those used to compute A161409.
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REFERENCES
| 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
| 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
| Sequence in context: A010961 A161690 * A162418 A010997 A163721 A177728
Adjacent sequences: A162180 A162181 A162182 * A162184 A162185 A162186
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KEYWORD
| nonn
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AUTHOR
| 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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