%I #12 Mar 30 2024 11:14:58
%S 1,2,6,21,74,237,668,1667,3750,7743,14898,27033,46698,77369,123672,
%T 191639,288998,425499,613278,867261,1205610,1650213,2227220,2967627,
%U 3907910,5090711,6565578,8389761,10629066,13358769
%N Number of permutations of length n which avoid the patterns 1243, 4132, 4321.
%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 114.
%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_08">Index entries for linear recurrences with constant coefficients</a>, signature (8,-28,56,-70,56,-28,8,-1).
%F G.f.: A(x) = -{(x^9-3x^8+3x^7-4x^6+19x^5-32x^4+27x^3-18x^2+6x-1)x}/{(x-1)^8}
%F For n >= 4, a(n) = (5n^6 - 84n^5 + 860n^4 - 5610n^3 + 22535n^2 - 49566n + 45900)/180. - Franklin T. Adams-Watters, Sep 16 2006
%t LinearRecurrence[{8,-28,56,-70,56,-28,8,-1},{1,2,6,21,74,237,668,1667,3750,7743},30] (* _Harvey P. Dale_, Mar 30 2024 *)
%K nonn,easy
%O 1,2
%A _Lara Pudwell_, Feb 26 2006