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%I #11 Jul 25 2018 11:40:25
%S 1,2,6,21,75,262,890,2949,9575,30590,96486,301269,933171,2872102,
%T 8794946,26822901,81539855,247232702,748061070,2259653349,6816525435,
%U 20540701510,61842968906,186063857829,559486534391,1681592864702
%N Number of permutations of length n which avoid the patterns 1243, 4123, 4213.
%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 160.
%H Lara Pudwell, <a href="http://faculty.valpo.edu/lpudwell/maple/webbook/bookmain.html">Systematic Studies in Pattern Avoidance</a>, 2005.
%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (8,-22,22,-1,-6).
%F G.f.: A(x) = -{(4x^4+5x^3-12x^2+6x-1)x}/{(x-1)(3x-1)(2x-1)(x^2+2x-1)}
%t LinearRecurrence[{8,-22,22,-1,-6},{1,2,6,21,75},40] (* _Harvey P. Dale_, Jul 25 2018 *)
%K nonn,easy
%O 1,2
%A _Lara Pudwell_, Feb 26 2006