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 A164954 #6 Nov 23 2016 18:28:36 %S A164954 1,21,420,8400,168000,3360000,67200000,1344000000,26879999790, %T A164954 537599991600,10751999748210,215039993288400,4300799832252000, %U A164954 86015995974720000,1720319906088000000,34406397853632000000 %N A164954 Number of reduced words of length n in Coxeter group on 21 generators S_i with relations (S_i)^2 = (S_i S_j)^8 = I. %C A164954 The initial terms coincide with those of A170740, although the two sequences are eventually different. %C A164954 Computed with MAGMA using commands similar to those used to compute A154638. %H A164954 <a href="/index/Rec#order_08">Index entries for linear recurrences with constant coefficients</a>, signature (19, 19, 19, 19, 19, 19, 19, -190). %F A164954 G.f. (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^8 - %F A164954 19*t^7 - 19*t^6 - 19*t^5 - 19*t^4 - 19*t^3 - 19*t^2 - 19*t + 1) %K A164954 nonn %O A164954 0,2 %A A164954 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009