

A161651


Number of reduced words of length n in the Weyl group A_38.


0



1, 38, 740, 9841, 100490, 840009, 5984563, 37358751, 208504842, 1056449420, 4918107194, 21239722205, 85769361157, 325992594164, 1172714551785, 4011922874670, 13106108017275, 41030950420668, 123490172703472
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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..18.


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: A269010 A010954 A035714 * A162166 A162392 A010990
Adjacent sequences: A161648 A161649 A161650 * A161652 A161653 A161654


KEYWORD

nonn


AUTHOR

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


STATUS

approved



