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 A169214 #12 May 10 2018 02:20:09
%S A169214 1,9,72,576,4608,36864,294912,2359296,18874368,150994944,1207959552,
%T A169214 9663676416,77309411328,618475290624,4947802324992,39582418599936,
%U A169214 316659348799488,2533274790395904,20266198323167232,162129586585337856
%N A169214 Number of reduced words of length n in Coxeter group on 9 generators S_i with relations (S_i)^2 = (S_i S_j)^28 = I.
%C A169214 The initial terms coincide with those of A003951, although the two sequences are eventually different.
%C A169214 First disagreement at index 28: a(28) = 21760664753063325144711132, A003951(28) = 21760664753063325144711168. - _Klaus Brockhaus_, May 24 2011
%C A169214 Computed with Magma using commands similar to those used to compute A154638.
%H A169214 <a href="/index/Rec#order_28">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, 7, -28).
%F A169214 G.f.: (t^28 + 2*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^28 - 7*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 A169214 coxG[{28,28,-7}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, May 01 2018 *)
%Y A169214 Cf. A003951 (G.f.: (1+x)/(1-8*x)).
%K A169214 nonn
%O A169214 0,2
%A A169214 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009