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 A168827 #14 Nov 24 2016 18:29:55
%S A168827 1,6,30,150,750,3750,18750,93750,468750,2343750,11718750,58593750,
%T A168827 292968750,1464843750,7324218750,36621093750,183105468750,
%U A168827 915527343750,4577636718750,22888183593750,114440917968735,572204589843600
%N A168827 Number of reduced words of length n in Coxeter group on 6 generators S_i with relations (S_i)^2 = (S_i S_j)^20 = I.
%C A168827 The initial terms coincide with those of A003948, although the two sequences are eventually different.
%C A168827 First disagreement at index 20: a(20) = 114440917968735, A003948(20) = 114440917968750. - _Klaus Brockhaus_, Apr 01 2011
%C A168827 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168827 G. C. Greubel, <a href="/A168827/b168827.txt">Table of n, a(n) for n = 0..1000</a>
%H A168827 <a href="/index/Rec#order_20">Index entries for linear recurrences with constant coefficients</a>, signature (4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, -10).
%F A168827 G.f.: (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)/(10*t^20 - 4*t^19 - 4*t^18 - 4*t^17 - 4*t^16 - 4*t^15 - 4*t^14 - 4*t^13 - 4*t^12 - 4*t^11 - 4*t^10 - 4*t^9 - 4*t^8 - 4*t^7 - 4*t^6 - 4*t^5 - 4*t^4 - 4*t^3 - 4*t^2 - 4*t + 1).
%t A168827 coxG[{20,10,-4,30}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Apr 26 2015 *)
%t A168827 CoefficientList[Series[(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)/(10*t^20 - 4*t^19 - 4*t^18 - 4*t^17 - 4*t^16 - 4*t^15 - 4*t^14 - 4*t^13 - 4*t^12 - 4*t^11 - 4*t^10 - 4*t^9 - 4*t^8 - 4*t^7 - 4*t^6 - 4*t^5 - 4*t^4 - 4*t^3 - 4*t^2 - 4*t + 1), {t,0,100}], t] (* _G. C. Greubel_, Nov 22 2016 *)
%Y A168827 Cf. A003948 (G.f.: (1+x)/(1-5*x)).
%K A168827 nonn
%O A168827 0,2
%A A168827 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009