A116830 - OEIS

%I #13 Nov 05 2025 15:22:05

%S 1,2,6,21,72,229,686,1972,5514,15131,40986,110013,293376,778678,

%T 2059646,5434009,14309508,37628165,98841306,259426800,680498610,

%U 1784183887,4676276006,12253079101,32099813532,84080037314,220207603686

%N Number of permutations of length n which avoid the patterns 1324, 2431, 4123.

%H D. Callan, T. Mansour, <a href="https://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 46.

%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 (7,-17,15,1,-7,2)

%F G.f.: A(x) = {(2x^6+3x^5+4x^4+2x^3-9x^2+5x-1)x}/{(x-1)(x^2-3x+1)(x^2-1+x)(2x-1)}

%F a(n) = 7*a(n-1) - 17*a(n-2) + 15*a(n-3) + a(n-4) - 7*a(n-5) + 2*a(n-6). - _Wesley Ivan Hurt_, Apr 18 2023

%K nonn,easy

%O 1,2

%A _Lara Pudwell_, Feb 26 2006