cp's OEIS Frontend

A169465 Number of reduced words of length n in Coxeter group on 20 generators S_i with relations (S_i)^2 = (S_i S_j)^33 = I.

%I A169465 #8 Nov 26 2016 07:21:11
%S A169465 1,20,380,7220,137180,2606420,49521980,940917620,17877434780,
%T A169465 339671260820,6453753955580,122621325156020,2329805177964380,
%U A169465 44266298381323220,841059669245141180,15980133715657682420
%N A169465 Number of reduced words of length n in Coxeter group on 20 generators S_i with relations (S_i)^2 = (S_i S_j)^33 = I.
%C A169465 The initial terms coincide with those of A170739, although the two sequences are eventually different.
%C A169465 Computed with MAGMA using commands similar to those used to compute A154638.
%H A169465 <a href="/index/Rec#order_33">Index entries for linear recurrences with constant coefficients</a>, signature (18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, 18, -171).
%F A169465 G.f. (t^33 + 2*t^32 + 2*t^31 + 2*t^30 + 2*t^29 + 2*t^28 + 2*t^27 + 2*t^26 +
%F A169465 2*t^25 + 2*t^24 + 2*t^23 + 2*t^22 + 2*t^21 + 2*t^20 + 2*t^19 + 2*t^18 +
%F A169465 2*t^17 + 2*t^16 + 2*t^15 + 2*t^14 + 2*t^13 + 2*t^12 + 2*t^11 + 2*t^10 +
%F A169465 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 +
%F A169465 1)/(171*t^33 - 18*t^32 - 18*t^31 - 18*t^30 - 18*t^29 - 18*t^28 - 18*t^27
%F A169465 - 18*t^26 - 18*t^25 - 18*t^24 - 18*t^23 - 18*t^22 - 18*t^21 - 18*t^20 -
%F A169465 18*t^19 - 18*t^18 - 18*t^17 - 18*t^16 - 18*t^15 - 18*t^14 - 18*t^13 -
%F A169465 18*t^12 - 18*t^11 - 18*t^10 - 18*t^9 - 18*t^8 - 18*t^7 - 18*t^6 - 18*t^5
%F A169465 - 18*t^4 - 18*t^3 - 18*t^2 - 18*t + 1)
%t A169465 coxG[{33,171,-18}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Jan 15 2015 *)
%K A169465 nonn
%O A169465 0,2
%A A169465 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009