cp's OEIS Frontend

A168871 Number of reduced words of length n in Coxeter group on 50 generators S_i with relations (S_i)^2 = (S_i S_j)^20 = I.

%I A168871 #8 Nov 24 2016 18:42:57
%S A168871 1,50,2450,120050,5882450,288240050,14123762450,692064360050,
%T A168871 33911153642450,1661646528480050,81420679895522450,
%U A168871 3989613314880600050,195491052429149402450,9579061569028320720050,469374016882387715282450
%N A168871 Number of reduced words of length n in Coxeter group on 50 generators S_i with relations (S_i)^2 = (S_i S_j)^20 = I.
%C A168871 The initial terms coincide with those of A170769, although the two sequences are eventually different.
%C A168871 First disagreement at index 20: a(20) = 6496740572356151005858607284921225, A170769(20) = 6496740572356151005858607284922450. - Klaus Brockhaus, Apr 04 2011
%C A168871 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168871 <a href="/index/Rec#order_20">Index entries for linear recurrences with constant coefficients</a>, signature (48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, -1176).
%F A168871 G.f.: (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)/(1176*t^20 - 48*t^19 - 48*t^18 - 48*t^17 - 48*t^16 - 48*t^15 - 48*t^14 - 48*t^13 - 48*t^12 - 48*t^11 - 48*t^10 - 48*t^9 - 48*t^8 - 48*t^7 - 48*t^6 - 48*t^5 - 48*t^4 - 48*t^3 - 48*t^2 - 48*t + 1).
%Y A168871 Cf. A170769 (G.f.: (1+x)/(1-49*x)).
%K A168871 nonn
%O A168871 0,2
%A A168871 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009