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 A166615 #11 Jun 22 2020 16:34:27
%S A166615 1,28,756,20412,551124,14880348,401769396,10847773692,292889889684,
%T A166615 7908027021468,213516729579636,5764951698650172,155653695863554266,
%U A166615 4202649788315954976,113471544284530509168,3063731695682316317568
%N A166615 Number of reduced words of length n in Coxeter group on 28 generators S_i with relations (S_i)^2 = (S_i S_j)^12 = I.
%C A166615 The initial terms coincide with those of A170747, although the two sequences are eventually different.
%C A166615 Computed with MAGMA using commands similar to those used to compute A154638.
%H A166615 G. C. Greubel, <a href="/A166615/b166615.txt">Table of n, a(n) for n = 0..500</a>
%H A166615 <a href="/index/Rec#order_12">Index entries for linear recurrences with constant coefficients</a>, signature (26, 26, 26, 26, 26, 26, 26, 26, 26, 26, 26, -351).
%F A166615 G.f.: (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)/(351*t^12 - 26*t^11 - 26*t^10 - 26*t^9 -26*t^8 -26*t^7 - 26*t^6 - 26*t^5 - 26*t^4 - 26*t^3 - 26*t^2 - 26*t +1).
%t A166615 CoefficientList[Series[(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)/(351*t^12 - 26*t^11 - 26*t^10 - 26*t^9 - 26*t^8 - 26*t^7 - 26*t^6 - 26*t^5 - 26*t^4 - 26*t^3 - 26*t^2 - 26*t + 1), {t, 0, 50}], t](* _G. C. Greubel_, May 19 2016 *)
%t A166615 coxG[{12,351,-26}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Jun 22 2020 *)
%K A166615 nonn
%O A166615 0,2
%A A166615 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009