

A161954


Number of reduced words of length n in the Weyl group B_27.


0



1, 27, 377, 3627, 27026, 166230, 878409, 4098483, 17222607, 66165501, 235124461, 780112671, 2435132466, 7196829486, 20245295242, 54455027238, 140596223184, 349621224120, 839832229131, 1953829030737, 4412447681628, 9693085025844
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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 II.)


LINKS

Table of n, a(n) for n=0..21.


FORMULA

G.f. for B_m is the polynomial Prod_{k=1..m}(1x^(2k))/(1x). Only finitely many terms are nonzero. This is a row of the triangle in A128084.


CROSSREFS

Sequence in context: A223205 A257786 A161530 * A162369 A231858 A162726
Adjacent sequences: A161951 A161952 A161953 * A161955 A161956 A161957


KEYWORD

nonn


AUTHOR

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


STATUS

approved



