%I #12 Apr 04 2017 03:15:05
%S 1,1,3,13,63,330,1838,10758,65586,413639,2684469,17852715,121256457,
%T 838843641,5897455515,42058344077,303787163823,2219452035639,
%U 16383022072549,122066094872139,917245868993865,6946236553301334,52979616083094066,406741647662973594
%N Number of indecomposable permutations avoiding the pattern 2143.
%H Vincenzo Librandi, <a href="/A284716/b284716.txt">Table of n, a(n) for n = 1..200</a>
%H A. L. L. Gao, S. Kitaev, P. B. Zhang. <a href="https://arxiv.org/abs/1605.05490">On pattern avoiding indecomposable permutations</a>, arXiv:1605.05490 [math.CO], 2016.
%F a(n) ~ 4 * 3^(2*n+1/2) / (Pi*n^4). - _Vaclav Kotesovec_, Apr 02 2017
%t Rest[CoefficientList[Series[2*x - 1 + (1-x)^2 * (1 + 5*x - (1-9*x)^(3/4) * (1-x)^(1/4) * HypergeometricPFQ[{-1/4, 3/4}, {1}, 64*x/((x-1)*(1-9*x)^3)])/(6*x^2), {x, 0, 30}], x]] (* _Vaclav Kotesovec_, Apr 02 2017 *)
%K nonn
%O 1,3
%A _N. J. A. Sloane_, Apr 02 2017
%E More terms from _Vaclav Kotesovec_, Apr 02 2017
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