A161662 Number of reduced words of length n in the Weyl group A_41.

1, 41, 860, 12299, 134848, 1208516, 9217866, 61521649, 366624707, 1980976460, 9822684102, 45131469838, 193676694825, 781450953227, 2981168796829, 10804753100301, 37358311880918, 123672795559348, 393238376839063

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: A010957 A346981 A299332 * A162178 A162403 A010993

Adjacent sequences: A161659 A161660 A161661 * A161663 A161664 A161665

Keyword

nonn

Author

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

Status

approved