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 A163988 #14 Sep 08 2022 08:45:47
%S A163988 1,22,462,9702,203742,4278582,89849991,1886844960,39623642520,
%T A163988 832094358480,17473936704840,366951729513600,7705966552789890,
%U A163988 161824882502745000,3398313815357307000,71364407061765925800
%N A163988 Number of reduced words of length n in Coxeter group on 22 generators S_i with relations (S_i)^2 = (S_i S_j)^6 = I.
%C A163988 The initial terms coincide with those of A170741, although the two sequences are eventually different.
%C A163988 Computed with MAGMA using commands similar to those used to compute A154638.
%H A163988 G. C. Greubel, <a href="/A163988/b163988.txt">Table of n, a(n) for n = 0..740</a>
%H A163988 <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (20, 20, 20, 20, 20, -210).
%F A163988 G.f.: (t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(210*t^6 - 20*t^5 - 20*t^4 - 20*t^3 - 20*t^2 - 20*t + 1).
%F A163988 G.f.: (1+x)*(1-x^6)/(1 -21*x +230*x^6 -210*x^7). - _G. C. Greubel_, Apr 25 2019
%t A163988 CoefficientList[Series[(1+x)*(1-x^6)/(1-21*x+230*x^6-210*x^7), {x,0,20}], x] (* _G. C. Greubel_, Aug 24 2017 *)
%t A163988 coxG[{6, 210, -20, 20}] (* The coxG program is at A169452 *)
%o A163988 (PARI) my(x='x+O('x^20)); Vec((1+x)*(1-x^6)/(1-21*x+230*x^6-210*x^7)) \\ _G. C. Greubel_, Aug 24 2017, modified Apr 25 2019
%o A163988 (Magma) R<x>:=PowerSeriesRing(Integers(), 20); Coefficients(R!( (1+x)*(1-x^6)/(1-21*x+230*x^6-210*x^7) )); // _G. C. Greubel_, Apr 25 2019
%o A163988 (Sage) ((1+x)*(1-x^6)/(1-21*x+230*x^6-210*x^7)).series(x, 20).coefficients(x, sparse=False) # _G. C. Greubel_, Apr 25 2019
%K A163988 nonn
%O A163988 0,2
%A A163988 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009