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A161690 Number of reduced words of length n in the Weyl group A_45. 0
1, 45, 1034, 16169, 193499, 1889589, 15678870, 113657422, 734546032, 4298041947, 23046526516, 114353850926, 529270561189, 2300298156544, 9441106933059, 36770120287103, 136464073495963, 484372497396274, 1649583299663734 (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 I.)

LINKS

Table of n, a(n) for n=0..18.

FORMULA

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

CROSSREFS

Sequence in context: A195466 A010961 A271795 * A162183 A162418 A010997

Adjacent sequences:  A161687 A161688 A161689 * A161691 A161692 A161693

KEYWORD

nonn

AUTHOR

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

STATUS

approved

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Last modified January 22 00:08 EST 2022. Contains 350481 sequences. (Running on oeis4.)