cp's OEIS Frontend

A169132 Number of reduced words of length n in Coxeter group on 23 generators S_i with relations (S_i)^2 = (S_i S_j)^26 = I.

%I A169132 #8 Nov 25 2016 12:18:59
%S A169132 1,23,506,11132,244904,5387888,118533536,2607737792,57370231424,
%T A169132 1262145091328,27767192009216,610878224202752,13439320932460544,
%U A169132 295665060514131968,6504631331310903296,143101889288839872512
%N A169132 Number of reduced words of length n in Coxeter group on 23 generators S_i with relations (S_i)^2 = (S_i S_j)^26 = I.
%C A169132 The initial terms coincide with those of A170742, although the two sequences are eventually different.
%C A169132 First disagreement at index 26: a(26) = 83617052878006826484668369192615683, A170742(26) = 83617052878006826484668369192615936. - Klaus Brockhaus, Apr 30 2011
%C A169132 Computed with MAGMA using commands similar to those used to compute A154638.
%H A169132 <a href="/index/Rec#order_26">Index entries for linear recurrences with constant coefficients</a>, signature (21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, 21, -231).
%F A169132 G.f.: (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)/(231*t^26 - 21*t^25 - 21*t^24 - 21*t^23 - 21*t^22 - 21*t^21 - 21*t^20 - 21*t^19 - 21*t^18 - 21*t^17 - 21*t^16 - 21*t^15 - 21*t^14 - 21*t^13 - 21*t^12 - 21*t^11 - 21*t^10 - 21*t^9 - 21*t^8 - 21*t^7 - 21*t^6 - 21*t^5 - 21*t^4 - 21*t^3 - 21*t^2 - 21*t + 1).
%Y A169132 Cf. A170742 (G.f.: (1+x)/(1-22*x)).
%K A169132 nonn
%O A169132 0,2
%A A169132 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009