A161571 - OEIS

%I #5 Jul 19 2015 10:32:12

%S 1,28,405,4031,31030,196882,1071637,5142716,22195440,87455155,

%T 318311627,1080299532,3445025535,10388772051,29784426945,81555340856,

%U 214122343813,540880490745,1318464472031,3109618390150,7112648815656,15810488782208

%N Number of reduced words of length n in the Weyl group A_28.

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

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

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

%F 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.

%K nonn

%O 0,2

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