A161977 - OEIS

%I #5 Jul 19 2015 10:24:00

%S 1,31,495,5425,45879,319145,1900920,9965384,46909324,201295028,

%T 796809245,2937251395,10161553364,33205476524,103050077489,

%U 305131440111,865481871426,2359754902590,6203436293890,15765840836350,38828731002622

%N Number of reduced words of length n in the Weyl group B_31.

%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