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 A162807 #7 May 02 2021 18:54:52 %S A162807 1,21,420,8190,159600,3108210,60532290,1178845500,22957618110, %T A162807 447091673490,8706955895400,169564956368010,3302218915041690, %U A162807 64309571936658300,1252406684472377910,24390187277913766890 %N A162807 Number of reduced words of length n in Coxeter group on 21 generators S_i with relations (S_i)^2 = (S_i S_j)^3 = I. %C A162807 The initial terms coincide with those of A170740, although the two sequences are eventually different. %C A162807 Computed with MAGMA using commands similar to those used to compute A154638. %H A162807 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (19, 19, -190). %F A162807 G.f.: (t^3 + 2*t^2 + 2*t + 1)/(190*t^3 - 19*t^2 - 19*t + 1). %F A162807 a(n) = 19*a(n-1)+19*a(n-2)-190*a(n-3). - _Wesley Ivan Hurt_, May 02 2021 %K A162807 nonn %O A162807 0,2 %A A162807 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009