cp's OEIS Frontend

A168916 Number of reduced words of length n in Coxeter group on 47 generators S_i with relations (S_i)^2 = (S_i S_j)^21 = I.

%I A168916 #8 Nov 25 2016 09:44:47
%S A168916 1,47,2162,99452,4574792,210440432,9680259872,445291954112,
%T A168916 20483429889152,942237774900992,43342937645445632,1993775131690499072,
%U A168916 91713656057762957312,4218828178657096036352,194066096218226417672192
%N A168916 Number of reduced words of length n in Coxeter group on 47 generators S_i with relations (S_i)^2 = (S_i S_j)^21 = I.
%C A168916 The initial terms coincide with those of A170766, although the two sequences are eventually different.
%C A168916 First disagreement at index 21: a(21) = 84577431398882274828535017711336391, A170766(21) = 84577431398882274828535017711337472. - Klaus Brockhaus, Apr 08 2011
%C A168916 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168916 <a href="/index/Rec#order_21">Index entries for linear recurrences with constant coefficients</a>, signature (45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, -1035).
%F A168916 G.f.: (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)/(1035*t^21 - 45*t^20 - 45*t^19 - 45*t^18 - 45*t^17 - 45*t^16 - 45*t^15 - 45*t^14 - 45*t^13 - 45*t^12 - 45*t^11 - 45*t^10 - 45*t^9 - 45*t^8 - 45*t^7 - 45*t^6 - 45*t^5 - 45*t^4 - 45*t^3 - 45*t^2 - 45*t + 1).
%Y A168916 Cf. A170766 (G.f.: (1+x)/(1-46*x)).
%K A168916 nonn
%O A168916 0,2
%A A168916 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009