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A161663 Number of reduced words of length n in the Weyl group A_42. 0
1, 42, 902, 13201, 148049, 1356565, 10574431, 72096080, 438720787, 2419697247, 12242381349, 57373851187, 251050546012, 1032501499239, 4013670296068, 14818423396369, 52176735277287, 175849530836635, 569087907675698 (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: A010958 A035716 A296011 * A162179 A162411 A010994

Adjacent sequences:  A161660 A161661 A161662 * A161664 A161665 A161666

KEYWORD

nonn

AUTHOR

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

STATUS

approved

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Last modified March 28 20:44 EDT 2020. Contains 333103 sequences. (Running on oeis4.)