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A161690
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Number of reduced words of length n in the Weyl group A_45.
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0
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1, 45, 1034, 16169, 193499, 1889589, 15678870, 113657422, 734546032, 4298041947, 23046526516, 114353850926, 529270561189, 2300298156544, 9441106933059, 36770120287103, 136464073495963, 484372497396274, 1649583299663734
(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 I.)
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FORMULA
| 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
| Sequence in context: A199352 A195466 A010961 * A162183 A162418 A010997
Adjacent sequences: A161687 A161688 A161689 * A161691 A161692 A161693
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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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