A162191 Number of reduced words of length n in the Weyl group B_47.

1, 47, 1127, 18377, 229171, 2330589, 20127092, 151775596, 1019876970, 6201909910, 34546227171, 177996721677, 855147273198, 3856508701234, 16418497039281, 66308104573247, 255104779810273, 938387762441199

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.