

A161476


Number of reduced words of length n in the Weyl group A_15.


0



1, 15, 119, 664, 2924, 10813, 34900, 100913, 266338, 650658, 1487262, 3208036, 6574987, 12876702, 24210652, 43874857, 76893687, 130701986, 216008661, 347854815, 546871981, 840732790, 1265769513, 1868715733, 2708503701
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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 PoincarĂ© polynomial.
N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche I.)


LINKS

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


FORMULA

G.f. for A_m is the polynomial Prod_{k=1..m}(1x^(k+1))/(1x). Only finitely many terms are nonzero. This is a row of the triangle in A008302.


CROSSREFS

Sequence in context: A331211 A183475 A253804 * A162321 A161875 A259746
Adjacent sequences: A161473 A161474 A161475 * A161477 A161478 A161479


KEYWORD

nonn


AUTHOR

John Cannon and N. J. A. Sloane, Nov 30 2009


STATUS

approved



