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 A167074 #12 Nov 24 2016 10:28:35
%S A167074 1,21,420,8400,168000,3360000,67200000,1344000000,26880000000,
%T A167074 537600000000,10752000000000,215040000000000,4300800000000000,
%U A167074 86015999999999790,1720319999999991600,34406399999999748210
%N A167074 Number of reduced words of length n in Coxeter group on 21 generators S_i with relations (S_i)^2 = (S_i S_j)^13 = I.
%C A167074 The initial terms coincide with those of A170740, although the two sequences are eventually different.
%C A167074 Computed with MAGMA using commands similar to those used to compute A154638.
%H A167074 G. C. Greubel, <a href="/A167074/b167074.txt">Table of n, a(n) for n = 0..500</a>
%H A167074 <a href="/index/Rec#order_13">Index entries for linear recurrences with constant coefficients</a>, signature (19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, 19, -190).
%F A167074 G.f.: (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)/(190*t^13 - 19*t^12 - 19*t^11 - 19*t^10 - 19*t^9 - 19*t^8 - 19*t^7 - 19*t^6 - 19*t^5 - 19*t^4 - 19*t^3 - 19*t^2 - 19*t + 1).
%t A167074 CoefficientList[Series[(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)/(190*t^13 - 19*t^12 - 19*t^11 - 19*t^10 - 19*t^9 - 19*t^8 - 19*t^7 - 19*t^6 - 19*t^5 - 19*t^4 - 19*t^3 - 19*t^2 - 19*t + 1), {t, 0, 50}], t] (* _G. C. Greubel_, May 31 2016 *)
%t A167074 coxG[{13,190,-19}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Sep 20 2016 *)
%K A167074 nonn
%O A167074 0,2
%A A167074 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009