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Number of reduced words of length n in Coxeter group on 24 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.
0

%I #9 Mar 23 2020 06:50:10

%S 1,24,552,12696,291732,6703488,154034496,3539441664,81330144060,

%T 1868823662376,42942280730712,986738081076264,22673505553878564,

%U 520997277758500752,11971601073631152624,275086336118245407888

%N Number of reduced words of length n in Coxeter group on 24 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.

%C The initial terms coincide with those of A170743, although the two sequences are eventually different.

%C Computed with MAGMA using commands similar to those used to compute A154638.

%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (22,22,22,-253).

%F G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(253*t^4 - 22*t^3 - 22*t^2 - 22*t + 1).

%t CoefficientList[Series[(t^4 + 2 t^3 + 2 t^2 + 2 t + 1)/(253 t^4 - 22 t^3 - 22 t^2 - 22 t + 1), {t, 0, 20}], t] (* _Jinyuan Wang_, Mar 23 2020 *)

%K nonn

%O 0,2

%A _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009