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 A168844 #10 Nov 24 2016 18:35:19
%S A168844 1,23,506,11132,244904,5387888,118533536,2607737792,57370231424,
%T A168844 1262145091328,27767192009216,610878224202752,13439320932460544,
%U A168844 295665060514131968,6504631331310903296,143101889288839872512
%N A168844 Number of reduced words of length n in Coxeter group on 23 generators S_i with relations (S_i)^2 = (S_i S_j)^20 = I.
%C A168844 The initial terms coincide with those of A170742, although the two sequences are eventually different.
%C A168844 First disagreement at index 20: a(20) = 737494475899422409853763331, A170742(20) = 737494475899422409853763584. - Klaus Brockhaus, Apr 02 2011
%C A168844 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168844 <a href="/index/Rec#order_20">Index entries for linear recurrences with constant coefficients</a>, signature (21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, -231).
%F A168844 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)/(231*t^20 - 21*t^19 - 21*t^18 - 21*t^17 - 21*t^16 - 21*t^15 - 21*t^14 - 21*t^13 - 21*t^12 - 21*t^11 - 21*t^10 - 21*t^9 - 21*t^8 - 21*t^7 - 21*t^6 - 21*t^5 - 21*t^4 - 21*t^3 - 21*t^2 - 21*t + 1).
%t A168844 coxG[{20,231,-21}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Dec 16 2014 *)
%Y A168844 Cf. A170742 (G.f.: (1+x)/(1-22*x)).
%K A168844 nonn
%O A168844 0,2
%A A168844 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009