A161933 Number of reduced words of length n in the Weyl group B_26.

1, 26, 350, 3250, 23399, 139204, 712179, 3220074, 13124124, 48942894, 168958960, 544988210, 1655019795, 4761697020, 13048465756, 34209731996, 86141195946, 209025000936, 490211005011, 1113996801606, 2458618650891, 5280637344216, 11057534183046, 22610808876996

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

Andrew Howroyd, Table of n, a(n) for n = 0..676

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

Row n=26 of A128084.

Sequence in context: A054938 A161526 A162368 * A225979 A162718 A010978

Adjacent sequences: A161930 A161931 A161932 * A161934 A161935 A161936

Keyword

nonn,fini,full

Author

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

Status

approved