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%I #12 Nov 05 2021 10:01:32
%S 1,1,2,6,21,73,247,821,2704,8868,29030,94960,310531,1015359,3319829,
%T 10854379,35488838,116031978,379370276,1240362982,4055405209,
%U 13259272613,43351600979,141739396705,463421329340,1515170329456,4953896123490,16196916164572,52956316947055,173142311541835
%N Number of permutations of [n] avoiding {2143, 3142, 1234}.
%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 2 No 111.
%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (7,-18,24,-19,9,-2).
%F 4*a(n) = n+1-n^2 -A175005(n) +A175005(n+1), n>0. - _R. J. Mathar_, Nov 05 2021
%p ((x^3-2*x^2+3*x-1)^2)/((2*x^3-3*x^2+4*x-1)*(x-1)^3) ;
%p taylor(%,x=0,40) ;
%p gfun[seriestolist](%) ;
%K nonn,easy
%O 0,3
%A _R. J. Mathar_, Nov 08 2017
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