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 A163171 #9 Mar 23 2020 06:49:50
%S A163171 1,23,506,11132,244651,5376756,118166433,2596973148,57074328696,
%T A163171 1254336803181,27566873759502,605844081921771,13314786972244758,
%U A163171 292622404684911840,6431035802682200787,141336482898202575984
%N A163171 Number of reduced words of length n in Coxeter group on 23 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.
%C A163171 The initial terms coincide with those of A170742, although the two sequences are eventually different.
%C A163171 Computed with MAGMA using commands similar to those used to compute A154638.
%H A163171 <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (21,21,21,-231).
%F A163171 G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(231*t^4 - 21*t^3 - 21*t^2 - 21*t + 1).
%t A163171 CoefficientList[Series[(t^4 + 2 t^3 + 2 t^2 + 2 t + 1)/(231 t^4 - 21 t^3 - 21 t^2 - 21 t + 1), {t, 0, 20}], t] (* _Jinyuan Wang_, Mar 23 2020 *)
%K A163171 nonn
%O A163171 0,2
%A A163171 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009