cp's OEIS Frontend

A168942 Number of reduced words of length n in Coxeter group on 25 generators S_i with relations (S_i)^2 = (S_i S_j)^22 = I.

%I A168942 #8 Nov 25 2016 09:54:02
%S A168942 1,25,600,14400,345600,8294400,199065600,4777574400,114661785600,
%T A168942 2751882854400,66045188505600,1585084524134400,38042028579225600,
%U A168942 913008685901414400,21912208461633945600,525893003079214694400
%N A168942 Number of reduced words of length n in Coxeter group on 25 generators S_i with relations (S_i)^2 = (S_i S_j)^22 = I.
%C A168942 The initial terms coincide with those of A170744, although the two sequences are eventually different.
%C A168942 First disagreement at index 22: a(22) = 2411993230704362204226492825300, A170744(22) = 2411993230704362204226492825600. - Klaus Brockhaus, Apr 10 2011
%C A168942 Computed with MAGMA using commands similar to those used to compute A154638.
%H A168942 <a href="/index/Rec#order_22">Index entries for linear recurrences with constant coefficients</a>, signature (23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, 23, -276).
%F A168942 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)/(276*t^22 - 23*t^21 - 23*t^20 - 23*t^19 - 23*t^18 - 23*t^17 - 23*t^16 - 23*t^15 - 23*t^14 - 23*t^13 - 23*t^12 - 23*t^11 - 23*t^10 - 23*t^9 - 23*t^8 - 23*t^7 - 23*t^6 - 23*t^5 - 23*t^4 - 23*t^3 - 23*t^2 - 23*t + 1).
%Y A168942 Cf. A170744 (G.f.: (1+x)/(1-24*x)).
%K A168942 nonn
%O A168942 0,2
%A A168942 _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009