A161930 Number of reduced words of length n in the Weyl group B_23.

1, 23, 275, 2277, 14673, 78407, 361514, 1477750, 5461235, 18518565, 58282576, 171815888, 477989151, 1262643305, 3183445871, 7694405993, 17895700206, 40182143330, 87349858045, 184297593435, 378236260170, 756560791350, 1477481301465, 2821499709615, 5276341352249

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

Andrew Howroyd, Table of n, a(n) for n = 0..529

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

Row n=23 of A128084.

Sequence in context: A142027 A161523 A162365 * A162680 A010975 A022588

Adjacent sequences: A161927 A161928 A161929 * A161931 A161932 A161933

Keyword

nonn,fini,full

Author

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

Status

approved