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Number of permutations of length n which avoid the patterns 1234, 4123, 4132.
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%I #9 Nov 08 2017 10:00:35

%S 1,2,6,21,76,263,843,2501,6941,18245,45928,111721,264482,612707,

%T 1394929,3131269,6948043,15269985,33290710,72085673,155182152,

%U 332387343,708820807,1505731877,3187639497,6727621949,14159916404,29729158217

%N Number of permutations of length n which avoid the patterns 1234, 4123, 4132.

%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 183.

%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 (10,-43,104,-155,146,-85,28,-4).

%F G.f.: A(x) = -{x(3x^7-20x^6+54x^5-71x^4+57x^3-29x^2+8x-1)}/{(2x-1)^2(x-1)^6}

%K nonn,easy

%O 1,2

%A _Lara Pudwell_, Feb 26 2006