

A162327


Number of reduced words of length n in the Weyl group D_16.


0



1, 16, 135, 800, 3739, 14672, 50252, 154224, 432174, 1121456, 2724183, 6248128, 13624922, 28409312, 56910017, 109964720, 205651974, 373334384, 659553420, 1136449488, 1913563930, 3154094352, 5096922202, 8086011920, 12609093085
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OFFSET

0,2


COMMENTS

Computed with MAGMA using commands similar to those used to compute A161409.


REFERENCES

N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche IV.)
J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See under Poincaré polynomial.


LINKS

Table of n, a(n) for n=0..24.


FORMULA

G.f. for D_m is the polynomial f(n) * Product( f(2i), i=1..n1 )/ f(1)^n, where f(k) = 1x^k. Only finitely many terms are nonzero. This is a row of the triangle in A162206.


CROSSREFS

Sequence in context: A237880 A284338 A161477 * A161876 A110274 A067814
Adjacent sequences: A162324 A162325 A162326 * A162328 A162329 A162330


KEYWORD

nonn


AUTHOR

John Cannon and N. J. A. Sloane, Dec 01 2009


STATUS

approved



