A161991 Number of reduced words of length n in the Weyl group B_34.

1, 34, 594, 7106, 65449, 494768, 3195983, 18134478, 92219577, 426746308, 1818523916, 7204803796, 26747139312, 93651006988, 310966484313, 983825011398, 2977708459669, 8652371731716, 24211251121429, 65420187465158

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

Table of n, a(n) for n=0..19.

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: A035712 A302955 A161647 * A162381 A010986 A232079

Adjacent sequences: A161988 A161989 A161990 * A161992 A161993 A161994

Keyword

nonn

Author

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

Status

approved