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A162328 Number of reduced words of length n in the Weyl group D_17. 32
1, 17, 152, 952, 4691, 19363, 69615, 223839, 656013, 1777469, 4501652, 10749780, 24374702, 52784014, 109694031, 219658751, 425310726, 798645125, 1458198664, 2594648817, 4508215686, 7662320971, 12759278753, 20845394645, 33454765680 (list; graph; refs; listen; history; text; internal format)
OFFSET
0,2
REFERENCES
N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche IV.)
J. E. Humphreys, Reflection Groups and Coxeter Groups, Cambridge, 1990. See under Poincaré polynomial.
LINKS
FORMULA
The growth series for D_k is the polynomial f(k)*Prod_{i=1..k-1} f(2*i), where f(m) = (1-x^m)/(1-x) [Corrected by N. J. A. Sloane, Aug 07 2021]. This is a row of the triangle in A162206.
MAPLE
# Growth series for D_k, truncated to terms of order M. - N. J. A. Sloane, Aug 07 2021
f := proc(m::integer) (1-x^m)/(1-x) ; end proc:
g := proc(k, M) local a, i; global f;
a:=f(k)*mul(f(2*i), i=1..k-1);
seriestolist(series(a, x, M+1));
end proc;
CROSSREFS
Sequence in context: A244852 A064102 A161497 * A161877 A221737 A139617
KEYWORD
nonn
AUTHOR
John Cannon and N. J. A. Sloane, Dec 01 2009
STATUS
approved

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Last modified February 21 04:08 EST 2024. Contains 370219 sequences. (Running on oeis4.)