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 A164638 #13 Feb 14 2017 00:29:21
%S A164638 1,25,600,14400,345600,8294400,199065600,4777574100,114661771200,
%T A164638 2751882336300,66045171931200,1585084026988800,38042014263091200,
%U A164638 913008285082828800,21912197468435340900,525892706277189044400
%N A164638 Number of reduced words of length n in Coxeter group on 25 generators S_i with relations (S_i)^2 = (S_i S_j)^7 = I.
%C A164638 The initial terms coincide with those of A170744, although the two sequences are eventually different.
%C A164638 Computed with MAGMA using commands similar to those used to compute A154638.
%H A164638 <a href="/index/Rec#order_07">Index entries for linear recurrences with constant coefficients</a>, signature (23, 23, 23, 23, 23, 23, -276).
%F A164638 G.f.: (t^7 + 2*t^6 + 2*t^5 + 2*t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(276*t^7 - 23*t^6 - 23*t^5 - 23*t^4 - 23*t^3 - 23*t^2 - 23*t + 1).
%t A164638 coxG[{7,276,-23}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Dec 05 2014 *)
%K A164638 nonn,easy
%O A164638 0,2
%A A164638 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009