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 A162949 Number of reduced words of length n in Coxeter group on 8 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I. 0

%I

%S 1,8,56,392,2716,18816,130368,903168,6257076,43348536,300314952,

%T 2080556856,14413923468,99858452400,691810982352,4792808455344,

%U 33204174947748,230035738812264,1593668302662744,11040800320974312

%N Number of reduced words of length n in Coxeter group on 8 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.

%C The initial terms coincide with those of A003950, although the two sequences are eventually different.

%C Computed with MAGMA using commands similar to those used to compute A154638.

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (6, 6, 6, -21).

%F G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(21*t^4 - 6*t^3 - 6*t^2 - 6*t + 1)

%t coxG[{4,21,-6}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, May 04 2018 *)

%K nonn

%O 0,2

%A _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009

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