A161695 Number of reduced words of length n in the Weyl group A_50.

1, 50, 1274, 22049, 291499, 3139085, 28673475, 228439966, 1619966516, 10384805691, 60915061181, 330167238726, 1666932807305, 7892136355680, 35239942525455, 149127876298179, 600620896491309, 2310803893154484

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..17.

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: A017766 A187459 A035720 * A162205 A162492 A017713

Adjacent sequences: A161692 A161693 A161694 * A161696 A161697 A161698

Keyword

nonn

Author

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

Status

approved