|
Search: id:A161716
|
|
|
| A161716 |
|
Number of reduced words of length n in the Weyl group B_7. |
|
+0
1
|
|
| 1, 7, 27, 77, 181, 371, 686, 1170, 1869, 2827, 4082, 5662, 7581, 9835, 12399, 15225, 18242, 21358, 24464, 27440, 30162, 32510, 34376, 35672, 36336, 36336, 35672, 34376, 32510, 30162, 27440, 24464, 21358, 18242, 15225, 12399, 9835, 7581, 5662
(list; graph; listen)
|
|
|
OFFSET
|
0,2
|
|
|
COMMENT
|
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 Poincare polynomial.
N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche II.)
|
|
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: A161439 A039623 A162210 this_sequence A162493 A005585 A161410
Adjacent sequences: A161713 A161714 A161715 this_sequence A161717 A161718 A161719
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
John Cannon (john(AT)maths.usyd.edu.au) and N. J. A. Sloane (njas(AT)research.att.com), Nov 30 2009
|
|
|
Search completed in 0.002 seconds
|
