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 A162300 Number of reduced words of length n in the Weyl group D_13. 32
 1, 13, 90, 442, 1728, 5720, 16653, 43745, 105586, 237354, 502113, 1007773, 1931631, 3554746, 6308706, 10837593, 18078112, 29360890, 46535840, 72124195, 109499325, 163097740, 238660747, 343506072, 486827392, 680018170, 937014482, 1274649714 (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; MATHEMATICA n = 13; x = y + y O[y]^(n^2); (1-x^n) Product[1-x^(2k), {k, 1, n-1}]/(1-x)^n // CoefficientList[#, y]& (* Jean-François Alcover, Mar 25 2020, from A162206 *) CROSSREFS Growth series for groups D_n, n = 3,...,32: A161435, A162207, A162208, A162209, A162210, A162211, A162212, A162248, A162288, A162297, A162300, A162301, A162321, A162327, A162328, A162346, A162347, A162359, A162360, A162364, A162365, A162366, A162367, A162368, A162369, A162370, A162376, A162377, A162378, A162379; also A162206 Sequence in context: A152867 A026912 A161465 * A161859 A057788 A267175 Adjacent sequences:  A162297 A162298 A162299 * A162301 A162302 A162303 KEYWORD nonn AUTHOR John Cannon and N. J. A. Sloane, Dec 01 2009 STATUS approved

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Last modified August 15 20:27 EDT 2022. Contains 356148 sequences. (Running on oeis4.)