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%I #11 Mar 23 2020 06:47:58
%S 1,19,342,6156,110637,1988388,35735751,642249324,11542621410,
%T 207446086881,3728258709552,67004941956759,1204224973728534,
%U 21642549713419572,388963830112221249,6990528525469894908,125635046969043641691,2257935858412484688900,40580032910411799982386
%N Number of reduced words of length n in Coxeter group on 19 generators S_i with relations (S_i)^2 = (S_i S_j)^4 = I.
%C The initial terms coincide with those of A170738, 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 (17,17,17,-153).
%F G.f.: (t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(153*t^4 - 17*t^3 - 17*t^2 - 17*t + 1).
%t coxG[{4,153,-17}] (* The coxG program is at A169452 *) (* _Harvey P. Dale_, Aug 24 2019 *)
%o (PARI) Vec((t^4 + 2*t^3 + 2*t^2 + 2*t + 1)/(153*t^4 - 17*t^3 - 17*t^2 - 17*t + 1) + O(t^20)) \\ _Jinyuan Wang_, Mar 23 2020
%K nonn
%O 0,2
%A _John Cannon_ and _N. J. A. Sloane_, Dec 03 2009
%E More terms from _Jinyuan Wang_, Mar 23 2020