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 A164635 #11 May 05 2021 10:07:49
%S A164635 1,22,462,9702,203742,4278582,89850222,1886854431,39623938200,
%T A164635 832102600560,17474152477320,366957157200480,7706099359922040,
%U A164635 161828066791314000,3398388987509621490,71366160020435695800
%N A164635 Number of reduced words of length n in Coxeter group on 22 generators S_i with relations (S_i)^2 = (S_i S_j)^7 = I.
%C A164635 The initial terms coincide with those of A170741, although the two sequences are eventually different.
%C A164635 Computed with MAGMA using commands similar to those used to compute A154638.
%H A164635 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (20, 20, 20, 20, 20, 20, -210).
%F A164635 G.f.: (t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(210*t^7 - 20*t^6 - 20*t^5 - 20*t^4 - 20*t^3 - 20*t^2 - 20*t + 1).
%F A164635 a(n) = -210*a(n-7) + 20*Sum_{k=1..6} a(n-k). - _Wesley Ivan Hurt_, May 05 2021
%t A164635 coxG[{7,210,-20}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Feb 11 2015 *)
%K A164635 nonn
%O A164635 0,2
%A A164635 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009