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 A284715 Number of indecomposable permutations avoiding the pattern 3214. 1
 1, 1, 3, 13, 65, 351, 1999, 11872, 73023, 462889, 3012162, 20056509, 136274564, 942624033, 6624531216, 47219125251, 340867497305, 2488891555146, 18361241675953, 136728796412286, 1026878910257061, 7772561249596928, 59253932922240432, 454708539839137050 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,3 LINKS Vincenzo Librandi, Table of n, a(n) for n = 1..200 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+7/2) * phi^2 / (16*Pi*n^4), where phi = A001622 = (1+sqrt(5))/2 is the golden ratio. - Vaclav Kotesovec, Apr 02 2017 MATHEMATICA 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 *) CROSSREFS Sequence in context: A200475 A106227 A256332 * A186577 A141342 A232222 Adjacent sequences:  A284712 A284713 A284714 * A284716 A284717 A284718 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 June 19 07:33 EDT 2019. Contains 324218 sequences. (Running on oeis4.)