A161465 Number of reduced words of length n in the Weyl group A_13.

1, 13, 90, 441, 1715, 5629, 16198, 41926, 99412, 218895, 452284, 884170, 1646177, 2934764, 5032235, 8330256, 13354639, 20789572, 31498907, 46541635, 67178356, 94865470, 131234038, 178050835, 237160055, 310405409, 399533919, 506084453, 631265833, 775831020, 939955265

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

Andrew Howroyd, Table of n, a(n) for n = 0..91

Formula

G.f. for A_m is the polynomial Product_{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

Row n=14 of A008302.

Sequence in context: A268746 A152867 A026912 * A162300 A161859 A057788

Adjacent sequences: A161462 A161463 A161464 * A161466 A161467 A161468

Keyword

nonn,fini,full

Author

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

Status

approved