%I #5 Jul 19 2015 10:22:12
%S 1,41,860,12300,134889,1209377,9230207,61657399,367846424,1990342376,
%T 9885562358,45508669878,195729780567,791712506207,3028721321382,
%U 11010682764150,38197208930405,126905454993645,405078061871575
%N Number of reduced words of length n in the Weyl group B_41.
%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