%I #5 Jul 19 2015 10:27:06
%S 1,13,90,442,1728,5720,16653,43745,105586,237354,502113,1007773,
%T 1931631,3554747,6308719,10837683,18078554,29362618,46541560,72140848,
%U 109543070,163203326,238898101,344008185,487835165,681949801,940569228,1280958420
%N Number of reduced words of length n in the Weyl group B_13.
%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
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