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%I #11 Nov 26 2017 13:59:32
%S 1,15,119,665,2939,10933,35580,103972,277950,689282,1602727,3523945,
%T 7376794,14784390,28500705,53054703,95687255,167682425,286219155,
%U 476896733,777117381,1240541355,1942863430,2989193690,4523359115
%N Number of reduced words of length n in the Weyl group B_15.
%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.)
%H Robert Israel, <a href="/A161875/b161875.txt">Table of n, a(n) for n = 0..225</a>
%F G.f. for B_m is the polynomial Product_{k=1..m}(1-x^(2k))/(1-x). Only finitely many terms are nonzero. This is a row of the triangle in A128084.
%p G:= normal(mul((1-x^(2*k))/(1-x), k=1..15)):
%p seq(coeff(G, x, j), j=0..15^2); # _Robert Israel_, Nov 26 2017
%K nonn,fini,full
%O 0,2
%A _John Cannon_ and _N. J. A. Sloane_, Nov 30 2009
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