%I #6 Nov 23 2016 22:10:07
%S 1,18,306,5202,88434,1503378,25557426,434476242,7386096114,
%T 125563633785,2134581771744,36287890075584,616894130535840,
%U 10487200206374784,178282403291884896,3030800852281773888,51523614426225577248
%N Number of reduced words of length n in Coxeter group on 18 generators S_i with relations (S_i)^2 = (S_i S_j)^9 = I.
%C The initial terms coincide with those of A170737, 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_09">Index entries for linear recurrences with constant coefficients</a>, signature (16, 16, 16, 16, 16, 16, 16, 16, -136).
%F 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 +
%F 1)/(136*t^9 - 16*t^8 - 16*t^7 - 16*t^6 - 16*t^5 - 16*t^4 - 16*t^3 -
%F 16*t^2 - 16*t + 1)
%K nonn
%O 0,2
%A _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009