A161679 Number of reduced words of length n in the Weyl group A_44.

1, 44, 989, 15135, 177330, 1696090, 13789281, 97978552, 620888610, 3563495915, 18748484569, 91307324410, 414916710263, 1771027595355, 7140808776515, 27329013354044, 99693953208860, 347908423900311, 1165210802267460

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 I.)

Links

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

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.

Crossrefs

Sequence in context: A010960 A035717 A035611 * A162182 A162413 A010996

Adjacent sequences: A161676 A161677 A161678 * A161680 A161681 A161682

Keyword

nonn

Author

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

Status

approved