cp's OEIS Frontend

A168922 Number of reduced words of length n in Coxeter group on 5 generators S_i with relations (S_i)^2 = (S_i S_j)^22 = I.

%I A168922 #8 Nov 25 2016 09:47:56
%S A168922 1,5,20,80,320,1280,5120,20480,81920,327680,1310720,5242880,20971520,
%T A168922 83886080,335544320,1342177280,5368709120,21474836480,85899345920,
%U A168922 343597383680,1374389534720,5497558138880,21990232555510,87960930222000
%N A168922 Number of reduced words of length n in Coxeter group on 5 generators S_i with relations (S_i)^2 = (S_i S_j)^22 = I.
%C A168922 The initial terms coincide with those of A003947, although the two sequences are eventually different.
%C A168922 First disagreement at index 22: a(22) = 21990232555510, A003947(22) = 21990232555520. - Klaus Brockhaus, Apr 09 2011
%C A168922 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168922 <a href="/index/Rec#order_22">Index entries for linear recurrences with constant coefficients</a>, signature (3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, -6).
%F A168922 G.f.: (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)/(6*t^22 - 3*t^21 - 3*t^20 - 3*t^19 - 3*t^18 - 3*t^17 - 3*t^16 - 3*t^15 - 3*t^14 - 3*t^13 - 3*t^12 - 3*t^11 - 3*t^10 - 3*t^9 - 3*t^8 - 3*t^7 - 3*t^6 - 3*t^5 - 3*t^4 - 3*t^3 - 3*t^2 - 3*t + 1).
%Y A168922 Cf. A003947 (G.f.: (1+x)/(1-4*x)).
%K A168922 nonn
%O A168922 0,2
%A A168922 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009