This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A169166 #10 Mar 22 2018 11:30:21
%S A169166 1,9,72,576,4608,36864,294912,2359296,18874368,150994944,1207959552,
%T A169166 9663676416,77309411328,618475290624,4947802324992,39582418599936,
%U A169166 316659348799488,2533274790395904,20266198323167232,162129586585337856
%N A169166 Number of reduced words of length n in Coxeter group on 9 generators S_i with relations (S_i)^2 = (S_i S_j)^27 = I.
%C A169166 The initial terms coincide with those of A003951, although the two sequences are eventually different.
%C A169166 First disagreement at index 27: a(27) = 2720083094132915643088860, A003951(27) = 2720083094132915643088896. - Klaus Brockhaus, May 07 2011
%C A169166 Computed with MAGMA using commands similar to those used to compute A154638.
%H A169166 <a href="/index/Rec#order_27">Index entries for linear recurrences with constant coefficients</a>, signature (7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, -28).
%F A169166 G.f.: (t^27 + 2*t^26 + 2*t^25 + 2*t^24 + 2*t^23 + 2*t^22 + 2*t^21 + 2*t^20 + 2*t^19 + 2*t^18 + 2*t^17 + 2*t^16 + 2*t^15 + 2*t^14 + 2*t^13 + 2*t^12 + 2*t^11 + 2*t^10 + 2*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^27 - 7*t^26 - 7*t^25 - 7*t^24 - 7*t^23 - 7*t^22 - 7*t^21 - 7*t^20 - 7*t^19 - 7*t^18 - 7*t^17 - 7*t^16 - 7*t^15 - 7*t^14 - 7*t^13 - 7*t^12 - 7*t^11 - 7*t^10 - 7*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).
%t A169166 coxG[{27,28,-7}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Mar 22 2018 *)
%Y A169166 Cf. A003951 (G.f.: (1+x)/(1-8*x)).
%K A169166 nonn
%O A169166 0,2
%A A169166 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009