A162181 Number of reduced words of length n in the Weyl group B_43.

1, 43, 945, 14147, 162238, 1519706, 12107381, 84352455, 524443953, 2954877827, 15270874059, 73095540169, 326649986846, 1371916939730, 5445905213996, 20530576252412, 73812456221233, 253999791183699, 839265188017740

Offset

0,2

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.)

Links

Table of n, a(n) for n=0..18.

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.

Crossrefs

Sequence in context: A157722 A010959 A161668 * A162412 A010995 A253915

Adjacent sequences: A162178 A162179 A162180 * A162182 A162183 A162184

Keyword

nonn

Author

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

Status

approved