A162205 Number of reduced words of length n in the Weyl group B_50.

1, 50, 1274, 22050, 291549, 3140360, 28695575, 228732790, 1623128975, 10413794040, 61146955156, 331819334000, 1677578203770, 7954932265700, 35582378559071, 150868021657130, 608916641370150, 2348116000139330, 8679467578139275, 30841029692445540, 105618977551474920

Offset

0,2

Comments

Computed with Magma using commands similar to those used to compute A161409.

References

N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche II.)

J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See under Poincaré polynomial.

Links

Table of n, a(n) for n=0..20.

Formula

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

Crossrefs

Cf. A128084.

Sequence in context: A035720 A161695 A162492 * A017713 A283311 A031602

Adjacent sequences: A162202 A162203 A162204 * A162206 A162207 A162208

Keyword

nonn,easy

Author

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

Status

approved