cp's OEIS Frontend

A168904 Number of reduced words of length n in Coxeter group on 35 generators S_i with relations (S_i)^2 = (S_i S_j)^21 = I.

%I A168904 #8 Nov 25 2016 09:41:22
%S A168904 1,35,1190,40460,1375640,46771760,1590239840,54068154560,
%T A168904 1838317255040,62502786671360,2125094746826240,72253221392092160,
%U A168904 2456609527331133440,83524723929258536960,2839840613594790256640,96554580862222868725760
%N A168904 Number of reduced words of length n in Coxeter group on 35 generators S_i with relations (S_i)^2 = (S_i S_j)^21 = I.
%C A168904 The initial terms coincide with those of A170754, although the two sequences are eventually different.
%C A168904 First disagreement at index 21: a(21) = 149157942900990975183742340955565, A170754(21) = 149157942900990975183742340956160. - Klaus Brockhaus, Apr 05 2011
%C A168904 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168904 <a href="/index/Rec#order_21">Index entries for linear recurrences with constant coefficients</a>, signature (33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, 33, -561).
%F A168904 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)/(561*t^21 - 33*t^20 - 33*t^19 - 33*t^18 - 33*t^17 - 33*t^16 - 33*t^15 - 33*t^14 - 33*t^13 - 33*t^12 - 33*t^11 - 33*t^10 - 33*t^9 - 33*t^8 - 33*t^7 - 33*t^6 - 33*t^5 - 33*t^4 - 33*t^3 - 33*t^2 - 33*t + 1).
%Y A168904 Cf. A170754 (G.f.: (1+x)/(1-34*x)).
%K A168904 nonn
%O A168904 0,2
%A A168904 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009