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 A169221 #12 May 10 2018 02:24:01
%S A169221 1,16,240,3600,54000,810000,12150000,182250000,2733750000,41006250000,
%T A169221 615093750000,9226406250000,138396093750000,2075941406250000,
%U A169221 31139121093750000,467086816406250000,7006302246093750000
%N A169221 Number of reduced words of length n in Coxeter group on 16 generators S_i with relations (S_i)^2 = (S_i S_j)^28 = I.
%C A169221 The initial terms coincide with those of A170735, although the two sequences are eventually different.
%C A169221 First disagreement at index 28: a(28) = 909042058585524559020996093749880, A170735(28) = 909042058585524559020996093750000. - _Klaus Brockhaus_, May 24 2011
%C A169221 Computed with Magma using commands similar to those used to compute A154638.
%H A169221 <a href="/index/Rec#order_28">Index entries for linear recurrences with constant coefficients</a>, signature (14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, 14, -105).
%F A169221 G.f.: (t^28 + 2*t^27 + 2*t^26 + 2*t^25 + 2*t^24 + 2*t^23 + 2*t^22 + 2*t^21 + 2*t^20 + 2*t^19 + 2*t^18 + 2*t^17 + 2*t^16 + 2*t^15 + 2*t^14 + 2*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)/(105*t^28 - 14*t^27 - 14*t^26 - 14*t^25 - 14*t^24 - 14*t^23 - 14*t^22 - 14*t^21 - 14*t^20 - 14*t^19 - 14*t^18 - 14*t^17 - 14*t^16 - 14*t^15 - 14*t^14 - 14*t^13 - 14*t^12 - 14*t^11 - 14*t^10 - 14*t^9 - 14*t^8 - 14*t^7 - 14*t^6 - 14*t^5 - 14*t^4 - 14*t^3 - 14*t^2 - 14*t + 1).
%t A169221 coxG[{28,105,-14}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Oct 20 2014 *)
%Y A169221 Cf. A170735 (G.f.: (1+x)/(1-15*x)).
%K A169221 nonn
%O A169221 0,2
%A A169221 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009