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 A161875 Number of reduced words of length n in the Weyl group B_15. 1
 1, 15, 119, 665, 2939, 10933, 35580, 103972, 277950, 689282, 1602727, 3523945, 7376794, 14784390, 28500705, 53054703, 95687255, 167682425, 286219155, 476896733, 777117381, 1240541355, 1942863430, 2989193690, 4523359115 (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 PoincarĂ© polynomial. N. Bourbaki, Groupes et alg. de Lie, Chap. 4, 5, 6. (The group is defined in Planche II.) LINKS Robert Israel, Table of n, a(n) for n = 0..225 FORMULA G.f. for B_m is the polynomial Product_{k=1..m}(1-x^(2k))/(1-x). Only finitely many terms are nonzero. This is a row of the triangle in A128084. MAPLE G:= normal(mul((1-x^(2*k))/(1-x), k=1..15)): seq(coeff(G, x, j), j=0..15^2); # Robert Israel, Nov 26 2017 CROSSREFS Sequence in context: A253804 A161476 A162321 * A259746 A139615 A196506 Adjacent sequences:  A161872 A161873 A161874 * A161876 A161877 A161878 KEYWORD nonn,fini,full AUTHOR John Cannon and N. J. A. Sloane, Nov 30 2009 STATUS approved

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Last modified November 26 07:49 EST 2020. Contains 338632 sequences. (Running on oeis4.)