cp's OEIS Frontend

A168932 Number of reduced words of length n in Coxeter group on 15 generators S_i with relations (S_i)^2 = (S_i S_j)^22 = I.

%I A168932 #11 Mar 15 2017 17:48:35
%S A168932 1,15,210,2940,41160,576240,8067360,112943040,1581202560,22136835840,
%T A168932 309915701760,4338819824640,60743477544960,850408685629440,
%U A168932 11905721598812160,166680102383370240,2333521433367183360
%N A168932 Number of reduced words of length n in Coxeter group on 15 generators S_i with relations (S_i)^2 = (S_i S_j)^22 = I.
%C A168932 The initial terms coincide with those of A170734, although the two sequences are eventually different.
%C A168932 First disagreement at index 22: a(22) = 17570333639309808327720855, A170734(22) = 17570333639309808327720960. - Klaus Brockhaus, Apr 09 2011
%C A168932 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168932 <a href="/index/Rec#order_22">Index entries for linear recurrences with constant coefficients</a>, signature (13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, 13, -91).
%F A168932 G.f.: (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)/(91*t^22 - 13*t^21 - 13*t^20 - 13*t^19 - 13*t^18 - 13*t^17 - 13*t^16 - 13*t^15 - 13*t^14 - 13*t^13 - 13*t^12 - 13*t^11 - 13*t^10 - 13*t^9 - 13*t^8 - 13*t^7 - 13*t^6 - 13*t^5 - 13*t^4 - 13*t^3 - 13*t^2 - 13*t + 1).
%t A168932 coxG[{22,91,-13}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Mar 15 2017 *)
%Y A168932 Cf. A170734 (G.f.: (1+x)/(1-14*x)).
%K A168932 nonn
%O A168932 0,2
%A A168932 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009