cp's OEIS Frontend

A169194 Number of reduced words of length n in Coxeter group on 37 generators S_i with relations (S_i)^2 = (S_i S_j)^27 = I.

%I A169194 #13 May 10 2018 02:11:24
%S A169194 1,37,1332,47952,1726272,62145792,2237248512,80540946432,
%T A169194 2899474071552,104381066575872,3757718396731392,135277862282330112,
%U A169194 4870003042163884032,175320109517899825152,6311523942644393705472
%N A169194 Number of reduced words of length n in Coxeter group on 37 generators S_i with relations (S_i)^2 = (S_i S_j)^27 = I.
%C A169194 The initial terms coincide with those of A170756, although the two sequences are eventually different.
%C A169194 First disagreement at index 27: a(27) = 1076630661583065728776661947808106342776166, A170756(27) = 1076630661583065728776661947808106342776832. - _Klaus Brockhaus_, May 07 2011
%C A169194 Computed with Magma using commands similar to those used to compute A154638.
%H A169194 <a href="/index/Rec#order_27">Index entries for linear recurrences with constant coefficients</a>, signature (35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, 35, -630).
%F A169194 G.f.: (t^27 + 2*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)/(630*t^27 - 35*t^26 - 35*t^25 - 35*t^24 - 35*t^23 - 35*t^22 - 35*t^21 - 35*t^20 - 35*t^19 - 35*t^18 - 35*t^17 - 35*t^16 - 35*t^15 - 35*t^14 - 35*t^13 - 35*t^12 - 35*t^11 - 35*t^10 - 35*t^9 - 35*t^8 - 35*t^7 - 35*t^6 - 35*t^5 - 35*t^4 - 35*t^3 - 35*t^2 - 35*t + 1).
%t A169194 With[{num=Total[2t^Range[26]]+t^27+1,den=Total[-35 t^Range[26]]+ 630t^27+ 1}, CoefficientList[Series[num/den,{t,0,30}],t]] (* _Harvey P. Dale_, Sep 28 2011 *)
%Y A169194 Cf. A170756 (G.f.: (1+x)/(1-36*x)).
%K A169194 nonn
%O A169194 0,2
%A A169194 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009