A161523 Number of reduced words of length n in the Weyl group A_23.

1, 23, 275, 2276, 14650, 78131, 359214, 1462801, 5380529, 18142125, 56724395, 165980490, 457927079, 1198603761, 2991929700, 7153857324, 16447016616, 36476745510, 78265410550, 162869776650, 329453055975, 649063995030, 1247641114021, 2343628878849, 4308300939450

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 I.)

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

Links

Andrew Howroyd, Table of n, a(n) for n = 0..276

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

Row n=24 of A008302.

Sequence in context: A142220 A257930 A142027 * A162365 A161930 A162680

Adjacent sequences: A161520 A161521 A161522 * A161524 A161525 A161526

Keyword

nonn,fini,full

Author

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

Status

approved