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 A168893 #10 May 31 2021 19:00:10
%S A168893 1,24,552,12696,292008,6716184,154472232,3552861336,81715810728,
%T A168893 1879463646744,43227663875112,994236269127576,22867434189934248,
%U A168893 525950986368487704,12096872686475217192,278228071788929995416
%N A168893 Number of reduced words of length n in Coxeter group on 24 generators S_i with relations (S_i)^2 = (S_i S_j)^21 = I.
%C A168893 The initial terms coincide with those of A170743, although the two sequences are eventually different.
%C A168893 First disagreement at index 21: a(21) = 41187739952030072230173484548, A170743(21) = 41187739952030072230173484824. - Klaus Brockhaus, Apr 05 2011
%C A168893 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168893 <a href="/index/Rec#order_21">Index entries for linear recurrences with constant coefficients</a>, signature (22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, 22, -253).
%F A168893 G.f.: (t^21 + 2*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)/(253*t^21 - 22*t^20 - 22*t^19 - 22*t^18 - 22*t^17 - 22*t^16 - 22*t^15 - 22*t^14 - 22*t^13 - 22*t^12 - 22*t^11 - 22*t^10 - 22*t^9 - 22*t^8 - 22*t^7 - 22*t^6 - 22*t^5 - 22*t^4 - 22*t^3 - 22*t^2 - 22*t + 1).
%t A168893 coxG[{21,253,-22}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, May 31 2021 *)
%Y A168893 Cf. A170743 (G.f.: (1+x)/(1-23*x)).
%K A168893 nonn
%O A168893 0,2
%A A168893 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009