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%I #5 Nov 23 2016 15:38:02
%S 1,9,72,576,4572,36288,288036,2286144,18145260,144020016,1143094932,
%T 9072809424,72011403324,571558593312,4536492984324,36006402202848,
%U 285784857170316,2268290625889680,18003551393278836,142895208872692080
%N Number of reduced words of length n in Coxeter group on 9 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.
%C The initial terms coincide with those of A003951, 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 (7, 7, 7, -28).
%F G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(28*t^4 - 7*t^3 - 7*t^2 - 7*t + 1)
%K nonn
%O 0,2
%A _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009
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