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%I #12 Nov 08 2017 04:20:22
%S 1,2,6,21,71,209,533,1205,2473,4696,8372,14169,22959,35855,54251,
%T 79865,114785,161518,223042,302861,405063,534381,696257,896909,
%U 1143401,1443716,1806832,2242801,2762831,3379371
%N Number of permutations of length n which avoid the patterns 2134, 3421, 4123.
%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 (2017), Table 2 No 22.
%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_07">Index entries for linear recurrences with constant coefficients</a>, signature (7,-21,35,-35,21,-7,1)
%F G.f.: A(x) = -{(x^6-8x^5+15x^4-14x^3+13x^2-5x+1)x}/{(x-1)^7}
%F (n^6 + 5n^5 - 55n^4 + 195n^3 - 186n^2 + 40n + 240)/240. - Franklin T. Adams-Watters, Sep 16 2006
%K nonn,easy
%O 1,2
%A _Lara Pudwell_, Feb 26 2006
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