|
%I #15 May 19 2019 13:27:48
%S 1,2,6,21,73,245,804,2617,8511,27709,90283,294231,958826,3124175,
%T 10178664,33160777,108030912,351937426,1146512182,3734982701,
%U 12167348792,39637060036,129123584284,420638265356,1370286347625
%N Number of permutations of length n which avoid the patterns 2413, 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 [math.CO] (2017), Table 2 No 110.
%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_09">Index entries for linear recurrences with constant coefficients</a>, signature (10,-42,100,-150,144,-86,27,-2,-1).
%F G.f.: (-x*(x^8+2x^7-18x^6+47x^5-65x^4+55x^3-28x^2+8x-1)) / (1+x^9+2x^8-27x^7+86x^6-144x^5+150x^4-100x^3+42x^2-10x). [Corrected by _Georg Fischer_, May 19 2019]
%t CoefficientList[Series[(-x*(x^8+2x^7-18x^6+47x^5-65x^4+55x^3-28x^2+8x-1)) / (1+x^9+2x^8-27x^7+86x^6-144x^5+150x^4-100x^3+42x^2-10x), {x, 0, 25}], x] (* _Georg Fischer_, May 19 2019 *)
%K nonn,easy
%O 1,2
%A _Lara Pudwell_, Feb 26 2006
|
