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A161512 Number of reduced words of length n in the Weyl group A_19. 0
1, 19, 189, 1310, 7105, 32110, 125761, 438407, 1386735, 4038090, 10947079, 27876345, 67163518, 154022930, 337879565, 712033264, 1446677555, 2842707951, 5417028610, 10034398370, 18106447251, 31885534341, 54889773721, 92505945904 (list; graph; refs; listen; history; text; internal format)
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
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: A327848 A034273 A193575 * A162347 A161879 A176600
KEYWORD
nonn
AUTHOR
John Cannon and N. J. A. Sloane, Nov 30 2009
STATUS
approved

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Last modified March 3 00:46 EST 2024. Contains 370499 sequences. (Running on oeis4.)