cp's OEIS Frontend

A168977 Number of reduced words of length n in Coxeter group on 12 generators S_i with relations (S_i)^2 = (S_i S_j)^23 = I.

%I A168977 #8 Nov 25 2016 10:22:05
%S A168977 1,12,132,1452,15972,175692,1932612,21258732,233846052,2572306572,
%T A168977 28295372292,311249095212,3423740047332,37661140520652,
%U A168977 414272545727172,4556998002998892,50126978032987812,551396758362865932
%N A168977 Number of reduced words of length n in Coxeter group on 12 generators S_i with relations (S_i)^2 = (S_i S_j)^23 = I.
%C A168977 The initial terms coincide with those of A003954, although the two sequences are eventually different.
%C A168977 First disagreement at index 23: a(23) = 976832992642077133359786, A003954(23) = 976832992642077133359852. - Klaus Brockhaus, Apr 19 2011
%C A168977 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168977 <a href="/index/Rec#order_23">Index entries for linear recurrences with constant coefficients</a>, signature (10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, 10, -55).
%F A168977 G.f.: (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)/(55*t^23 - 10*t^22 - 10*t^21 - 10*t^20 - 10*t^19 - 10*t^18 - 10*t^17 - 10*t^16 - 10*t^15 - 10*t^14 - 10*t^13 - 10*t^12 - 10*t^11 - 10*t^10 - 10*t^9 - 10*t^8 - 10*t^7 - 10*t^6 - 10*t^5 - 10*t^4 - 10*t^3 - 10*t^2 - 10*t + 1).
%Y A168977 Cf. A003954 (G.f.: (1+x)/(1-11*x)).
%K A168977 nonn
%O A168977 0,2
%A A168977 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009