cp's OEIS Frontend

A168959 Number of reduced words of length n in Coxeter group on 42 generators S_i with relations (S_i)^2 = (S_i S_j)^22 = I.

%I A168959 #8 Nov 25 2016 10:06:48
%S A168959 1,42,1722,70602,2894682,118681962,4865960442,199504378122,
%T A168959 8179679503002,335366859623082,13750041244546362,563751691026400842,
%U A168959 23113819332082434522,947666592615379815402,38854330297230572431482
%N A168959 Number of reduced words of length n in Coxeter group on 42 generators S_i with relations (S_i)^2 = (S_i S_j)^22 = I.
%C A168959 The initial terms coincide with those of A170761, although the two sequences are eventually different.
%C A168959 First disagreement at index 22: a(22) = 310248922250956840604217394923586461, A170761(22) = 310248922250956840604217394923587322. - Klaus Brockhaus, Apr 10 2011
%C A168959 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168959 <a href="/index/Rec#order_22">Index entries for linear recurrences with constant coefficients</a>, signature (40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, 40, -820).
%F A168959 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)/(820*t^22 - 40*t^21 - 40*t^20 - 40*t^19 - 40*t^18 - 40*t^17 - 40*t^16 - 40*t^15 - 40*t^14 - 40*t^13 - 40*t^12 - 40*t^11 - 40*t^10 - 40*t^9 - 40*t^8 - 40*t^7 - 40*t^6 - 40*t^5 - 40*t^4 - 40*t^3 - 40*t^2 - 40*t + 1).
%Y A168959 Cf. A170761 (G.f.: (1+x)/(1-41*x)).
%K A168959 nonn
%O A168959 0,2
%A A168959 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009