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 A168809 #15 Nov 24 2016 16:24:17
%S A168809 1,36,1260,44100,1543500,54022500,1890787500,66177562500,
%T A168809 2316214687500,81067514062500,2837362992187500,99307704726562500,
%U A168809 3475769665429687500,121651938290039062500,4257817840151367187500,149023624405297851562500
%N A168809 Number of reduced words of length n in Coxeter group on 36 generators S_i with relations (S_i)^2 = (S_i S_j)^19 = I.
%C A168809 The initial terms coincide with those of A170755, although the two sequences are eventually different.
%C A168809 First disagreement at index 19: a(19) = 223628576373200088500976561870, A170755(19) = 223628576373200088500976562500. - _Klaus Brockhaus_, Apr 01 2011
%C A168809 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168809 G. C. Greubel, <a href="/A168809/b168809.txt">Table of n, a(n) for n = 0..500</a>
%H A168809 <a href="/index/Rec#order_19">Index entries for linear recurrences with constant coefficients</a>, signature (34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, 34, -595).
%F A168809 G.f.: (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)/(595*t^19 - 34*t^18 - 34*t^17 - 34*t^16 - 34*t^15 - 34*t^14 - 34*t^13 - 34*t^12 - 34*t^11 - 34*t^10 - 34*t^9 - 34*t^8 - 34*t^7 - 34*t^6 - 34*t^5 - 34*t^4 - 34*t^3 - 34*t^2 - 34*t + 1).
%t A168809 With[{num=Total[2t^Range[18]]+t^19+1,den=Total[-34 t^Range[18]]+ 595t^19+ 1},CoefficientList[Series[num/den,{t,0,20}],t]] (* _Harvey P. Dale_, Aug 11 2011 *)
%t A168809 CoefficientList[Series[(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)/(595*t^19 - 34*t^18 - 34*t^17 - 34*t^16 - 34*t^15 - 34*t^14 - 34*t^13 - 34*t^12 - 34*t^11 - 34*t^10 - 34*t^9 - 34*t^8 - 34*t^7 - 34*t^6 - 34*t^5 - 34*t^4 - 34*t^3 - 34*t^2 - 34*t + 1), {t, 0, 50}], t] (* _G. C. Greubel_, Aug 17 2016 *)
%Y A168809 Cf. A170755 (G.f.: (1+x)/(1-35*x)).
%K A168809 nonn
%O A168809 0,2
%A A168809 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009