A161668 Number of reduced words of length n in the Weyl group A_43.

1, 43, 945, 14146, 162195, 1518760, 12093191, 84189271, 522910058, 2942607305, 15184988654, 72558839841, 323609385853, 1356110885092, 5369781181160, 20188204577529, 72364939854816, 248214470691451, 817302378367149

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: A332910 A157722 A010959 * A162181 A162412 A010995

Adjacent sequences: A161665 A161666 A161667 * A161669 A161670 A161671

Keyword

nonn

Author

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

Status

approved