A161649 Number of reduced words of length n in the Weyl group A_36.

1, 36, 665, 8399, 81548, 648870, 4405035, 26229634, 139771903, 676798487, 3013713196, 12459957237, 48208023941, 175693594055, 606498724614, 1992486365264, 6254976819720, 18830657260788, 54534379879411

Offset

0,2

Comments

Computed with MAGMA using commands similar to those used to compute A161409.

References

N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche I.)

J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See under Poincaré polynomial.

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: A231767 A278277 A188305 * A162150 A162388 A010988

Adjacent sequences: A161646 A161647 A161648 * A161650 A161651 A161652

Keyword

nonn

Author

_John Cannon_ and _N. J. A. Sloane_, Nov 30 2009

Status

approved