A161692 Number of reduced words of length n in the Weyl group A_47.

1, 47, 1127, 18376, 229124, 2329461, 20108668, 151545297, 1017527958, 6181552566, 34392103690, 176956505740, 848791468979, 3820924588762, 16234164641604, 65417524981549, 251064958817457, 921084890049639

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..17.

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: A012018 A010963 A234354 * A162191 A162456 A010999

Adjacent sequences: A161689 A161690 A161691 * A161693 A161694 A161695

Keyword

nonn

Author

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

Status

approved