A161988 Number of reduced words of length n in the Weyl group B_33.

1, 33, 560, 6512, 58343, 429319, 2701215, 14938495, 74085099, 334526731, 1391777608, 5386279880, 19542335516, 66903867676, 217315477325, 672858527085, 1993883448271, 5674663272047, 15558879389713, 41208936343729

Offset: 0

Author

John Cannon and N. J. A. Sloane, Nov 30 2009

Keywords

• nonn

Comments

Computed with MAGMA using commands similar to those used to compute A161409.

References

• J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See under Poincaré polynomial.
• N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche II.)

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.