%I #5 Jul 19 2015 10:22:01
%S 1,42,902,13202,148091,1357468,10587675,72245074,440091498,2430433874,
%T 12315996232,57824666110,253554446677,1045266952884,4073988274266,
%U 15084671038416,53281879968821,180187334962466,585265396834041
%N Number of reduced words of length n in the Weyl group B_42.
%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 II.)
%F G.f. for B_m is the polynomial Prod_{k=1..m}(1-x^(2k))/(1-x). Only finitely many terms are nonzero. This is a row of the triangle in A128084.
%K nonn
%O 0,2
%A _John Cannon_ and _N. J. A. Sloane_, Nov 30 2009