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 A165216 Number of reduced words of length n in Coxeter group on 9 generators S_i with relations (S_i)^2 = (S_i S_j)^9 = I. 0
 1, 9, 72, 576, 4608, 36864, 294912, 2359296, 18874368, 150994908, 1207958976, 9663669540, 77309338176, 618474560256, 4947795320832, 39582353276928, 316658751897600, 2533269420638208, 20266150608766188, 162129166819422768 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS The initial terms coincide with those of A003951, although the two sequences are eventually different. Computed with MAGMA using commands similar to those used to compute A154638. LINKS Index entries for linear recurrences with constant coefficients, signature (7, 7, 7, 7, 7, 7, 7, 7, -28). FORMULA G.f. (t^9 + 2*t^8 + 2*t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(28*t^9 - 7*t^8 - 7*t^7 - 7*t^6 - 7*t^5 - 7*t^4 - 7*t^3 - 7*t^2 - 7*t + 1) MATHEMATICA With[{num=Total[2t^Range]+t^9+1, den=Total[-7 t^Range]+ 28t^9+1}, CoefficientList[Series[num/den, {t, 0, 30}], t]] (* Harvey P. Dale, Oct 02 2011 *) CROSSREFS Sequence in context: A163953 A164375 A164777 * A165787 A166367 A166541 Adjacent sequences:  A165213 A165214 A165215 * A165217 A165218 A165219 KEYWORD nonn AUTHOR John Cannon and N. J. A. Sloane, Dec 03 2009 STATUS approved

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Last modified September 15 18:22 EDT 2019. Contains 327082 sequences. (Running on oeis4.)