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A161879 Number of reduced words of length n in the Weyl group B_19. 1
1, 19, 189, 1311, 7124, 32300, 127091, 445721, 1420364, 4172476, 11426240, 29429784, 71808030, 166970290, 371826581, 796341623, 1646167391, 3294638285, 6401307860, 12102626404, 22312161586, 40184022430, 70815181390 (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
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.
CROSSREFS
Sequence in context: A193575 A161512 A162347 * A176600 A139619 A121039
KEYWORD
nonn
AUTHOR
John Cannon and N. J. A. Sloane, Nov 30 2009
STATUS
approved

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Last modified March 2 06:08 EST 2024. Contains 370460 sequences. (Running on oeis4.)