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A284719
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Number of indecomposable permutations avoiding the pattern 1234.
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0
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1, 1, 3, 13, 69, 400, 2390, 14545, 90285, 572801, 3715919, 24627773, 166497633, 1146141359, 8019377521, 56936916951, 409590294555, 2981507133559, 21935750057293, 162953508604187, 1221207542430487, 9225662325264922, 70209599158600184, 537934680500809021
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OFFSET
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1,3
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LINKS
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FORMULA
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MATHEMATICA
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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 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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