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A284715
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Number of indecomposable permutations avoiding the pattern 3214.
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1
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1, 1, 3, 13, 65, 351, 1999, 11872, 73023, 462889, 3012162, 20056509, 136274564, 942624033, 6624531216, 47219125251, 340867497305, 2488891555146, 18361241675953, 136728796412286, 1026878910257061, 7772561249596928, 59253932922240432, 454708539839137050
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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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a(n) ~ 3^(2*n+7/2) * phi^2 / (16*Pi*n^4), where phi = A001622 = (1+sqrt(5))/2 is the golden ratio. - Vaclav Kotesovec, Apr 02 2017
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MATHEMATICA
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Rest[CoefficientList[Series[1/2*(Sqrt[1-4*x] + 1)*((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), {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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