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 A163124 #7 Nov 23 2016 15:41:13
%S A163124 1,20,380,7220,136990,2599200,49316400,935712000,17753871510,
%T A163124 336855735180,6391382632020,121267853544780,2300893742387430,
%U A163124 43656351283440360,828320305398630840,15716259104684097960
%N A163124 Number of reduced words of length n in Coxeter group on 20 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.
%C A163124 The initial terms coincide with those of A170739, although the two sequences are eventually different.
%C A163124 Computed with MAGMA using commands similar to those used to compute A154638.
%H A163124 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (18, 18, 18, -171).
%F A163124 G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(171*t^4 - 18*t^3 - 18*t^2 - 18*t + 1)
%t A163124 coxG[{4,171,-18}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Dec 14 2015 *)
%K A163124 nonn
%O A163124 0,2
%A A163124 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009