A116763 - OEIS

%I #9 Nov 08 2017 09:47:09

%S 1,2,6,21,75,255,813,2443,6985,19175,50917,131555,332257,823263,

%T 2007005,4825051,11460569,26935255,62717909,144834515,332005329,

%U 756023247,1711275981,3852468171,8629780425,19243466695,42731569093,94522834883

%N Number of permutations of length n which avoid the patterns 2134, 3241, 3421.

%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 145.

%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_06">Index entries for linear recurrences with constant coefficients</a>, signature (10,-41,88,-104,64,-16)

%F G.f.: A(x) = {x(2x^6-18x^5+39x^4-45x^3+27x^2-8x+1)}/{(x-1)^2(2x-1)^4}

%K nonn,easy

%O 1,2

%A _Lara Pudwell_, Feb 26 2006