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%I #13 Oct 26 2017 02:58:42
%S 1,1,3,13,69,400,2390,14545,90285,572801,3715919,24627773,166497633,
%T 1146141359,8019377521,56936916951,409590294555,2981507133559,
%U 21935750057293,162953508604187,1221207542430487,9225662325264922,70209599158600184,537934680500809021
%N Number of indecomposable permutations avoiding the pattern 1234.
%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) ~ 3^(2*n+9/2) / (16*Pi*n^4). - _Vaclav Kotesovec_, Apr 02 2017
%t Rest[CoefficientList[Series[(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) - (1 - Sqrt[1-4*x])/(1-x) + x^3/(1-x)^3 + x^2/(1-x)^2 + 2*x/(1-x) - 1, {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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