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%I #6 Mar 21 2021 21:24:04
%S 1,1,2,6,21,77,283,1032,3740,13522,48930,177564,646908,2367121,
%T 8699706,32108614,118975273,442467434,1651076429,6180073782,
%U 23197995681,87304824502,329357941951,1245262325246,4717865597299,17908489016748,68099538024617,259388123347450,989533568712759
%N Number of permutations of [n] avoiding {1243, 1324, 2431}.
%H D. Callan, T. Mansour, <a href="http://arxiv.org/abs/1705.00933">Enumeration of small Wilf classes avoiding 1324 and two other 4-letter patterns</a>, arXiv:1705.00933 [math.CO] (2017), Table 1 No 210.
%p C := (1-sqrt(1-4*x))/2/x ;
%p (1 -6*x +13*x^2 -11*x^3 +4*x^4)/(x^2*(1 -x)^2)*C -(1 -6*x +12*x^2 -8*x^3 +2*x^4)/(x^2*(1 -x)*(1 -2*x)) ;
%p taylor(%,x=0,40) ;
%p gfun[seriestolist](%) ;
%K nonn,easy
%O 0,3
%A _R. J. Mathar_, Nov 09 2017
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