A161647 Number of reduced words of length n in the Weyl group A_34.

1, 34, 594, 7105, 65415, 494173, 3188843, 18068434, 91717670, 423484315, 1799888125, 7109329332, 26301822663, 91737503410, 303319560445, 955182510091, 2876502813806, 8313189986612, 23128042177555, 62110520140315

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..19.

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: A126924 A035712 A302955 * A161991 A162381 A010986

Adjacent sequences: A161644 A161645 A161646 * A161648 A161649 A161650

Keyword

nonn

Author

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

Status

approved