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 A163967 Number of reduced words of length n in Coxeter group on 18 generators S_i with relations (S_i)^2 = (S_i S_j)^6 = I. 1
 1, 18, 306, 5202, 88434, 1503378, 25557273, 434471040, 7385963616, 125560632384, 2134518016032, 36286589786112, 616868346117816, 10486699320193920, 178272824864888448, 3030619941978033024, 51520231643134128768 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The initial terms coincide with those of A170737, although the two sequences are eventually different. Computed with MAGMA using commands similar to those used to compute A154638. LINKS G. C. Greubel, Table of n, a(n) for n = 0..800 Index entries for linear recurrences with constant coefficients, signature (16, 16, 16, 16, 16, -136). FORMULA G.f.: (t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(136*t^6 - 16*t^5 - 16*t^4 - 16*t^3 - 16*t^2 - 16*t + 1). MATHEMATICA CoefficientList[Series[(t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(136*t^6 - 16*t^5 - 16*t^4 - 16*t^3 - 16*t^2 - 16*t + 1), {t, 0, 50}], t] (* G. C. Greubel, Aug 23 2017 *) PROG (PARI) t='t+O('t^50); Vec((t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(136*t^6 - 16*t^5 - 16*t^4 - 16*t^3 - 16*t^2 - 16*t + 1)) \\ G. C. Greubel, Aug 23 2017 CROSSREFS Sequence in context: A097831 A163104 A163452 * A164630 A164892 A165329 Adjacent sequences:  A163964 A163965 A163966 * A163968 A163969 A163970 KEYWORD nonn AUTHOR John Cannon and N. J. A. Sloane, Dec 03 2009 STATUS approved

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Last modified June 17 15:28 EDT 2019. Contains 324194 sequences. (Running on oeis4.)