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A161876 Number of reduced words of length n in the Weyl group B_16. 1
1, 16, 135, 800, 3739, 14672, 50252, 154224, 432174, 1121456, 2724183, 6248128, 13624922, 28409312, 56910017, 109964720, 205651975, 373334400, 659553555, 1136450288, 1913567669, 3154109024, 5096972454, 8086166144, 12609525259 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
COMMENTS
Computed with MAGMA using commands similar to those used to compute A161409.
REFERENCES
J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See under Poincaré polynomial.
N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche II.)
LINKS
Robert Israel, Table of n, a(n) for n = 0..256 (complete sequence)
FORMULA
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.
MAPLE
G:= normal(mul((1-x^(2*k))/(1-x), k=1..16)):
seq(coeff(G, x, j), j=0..256); # Robert Israel, Mar 31 2017
CROSSREFS
Sequence in context: A284338 A161477 A162327 * A110274 A067814 A219904
KEYWORD
nonn,fini,full
AUTHOR
John Cannon and N. J. A. Sloane, Nov 30 2009
STATUS
approved

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Last modified February 24 05:54 EST 2024. Contains 370294 sequences. (Running on oeis4.)