

A161662


Number of reduced words of length n in the Weyl group A_41.


0



1, 41, 860, 12299, 134848, 1208516, 9217866, 61521649, 366624707, 1980976460, 9822684102, 45131469838, 193676694825, 781450953227, 2981168796829, 10804753100301, 37358311880918, 123672795559348, 393238376839063
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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 PoincarĂ© polynomial.
N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche I.)


LINKS

Table of n, a(n) for n=0..18.


FORMULA

G.f. for A_m is the polynomial Prod_{k=1..m}(1x^(k+1))/(1x). Only finitely many terms are nonzero. This is a row of the triangle in A008302.


CROSSREFS

Sequence in context: A087856 A010957 A299332 * A162178 A162403 A010993
Adjacent sequences: A161659 A161660 A161661 * A161663 A161664 A161665


KEYWORD

nonn


AUTHOR

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


STATUS

approved



