A161879 - OEIS

%I #5 Jul 19 2015 10:25:55

%S 1,19,189,1311,7124,32300,127091,445721,1420364,4172476,11426240,

%T 29429784,71808030,166970290,371826581,796341623,1646167391,

%U 3294638285,6401307860,12102626404,22312161586,40184022430,70815181390

%N Number of reduced words of length n in the Weyl group B_19.

%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