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Number of reduced words of length n in the Weyl group B_45.
0

%I #5 Jul 19 2015 10:21:26

%S 1,45,1034,16170,193544,1890624,15695085,113852001,736452870,

%T 4313931566,23162284321,115106177245,533700057015,2324210876515,

%U 9560626910011,37327619195919,138907067703060,494486307393900,1689330735102480

%N Number of reduced words of length n in the Weyl group B_45.

%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