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Search: id:A162288
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| A162288 |
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Number of reduced words of length n in the Weyl group D_11. |
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+0
2
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| 1, 11, 65, 275, 934, 2706, 6941, 16159, 34749, 69927, 132991, 240900, 418187, 699193, 1130581, 1774058, 2709201, 4036252, 5878719, 8385597, 11733007, 16125043, 21793619, 28997122, 38017704, 49157086, 62730799, 79060850
(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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N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche IV.)
J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See under Poincare polynomial.
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FORMULA
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G.f. for D_m is the polynomial f(n) * Product( f(2i), i=1..n-1 )/ f(1)^n, where f(k) = 1-x^k. Only finitely many terms are nonzero. This is a row of the triangle in A162206.
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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), Dec 01 2009
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