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 A284719 Number of indecomposable permutations avoiding the pattern 1234. 0
 1, 1, 3, 13, 69, 400, 2390, 14545, 90285, 572801, 3715919, 24627773, 166497633, 1146141359, 8019377521, 56936916951, 409590294555, 2981507133559, 21935750057293, 162953508604187, 1221207542430487, 9225662325264922, 70209599158600184, 537934680500809021 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS A. L. L. Gao, S. Kitaev, P. B. Zhang. On pattern avoiding indecomposable permutations, arXiv:1605.05490 [math.CO], 2016. FORMULA a(n) ~ 3^(2*n+9/2) / (16*Pi*n^4). - Vaclav Kotesovec, Apr 02 2017 MATHEMATICA 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 *) CROSSREFS Sequence in context: A058307 A020107 A284718 * A128079 A074534 A153395 Adjacent sequences:  A284716 A284717 A284718 * A284720 A284721 A284722 KEYWORD nonn AUTHOR N. J. A. Sloane, Apr 02 2017 EXTENSIONS More terms from Vaclav Kotesovec, Apr 02 2017 STATUS approved

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Last modified May 23 13:32 EDT 2019. Contains 323514 sequences. (Running on oeis4.)