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A284716
Number of indecomposable permutations avoiding the pattern 2143.
1
1, 1, 3, 13, 63, 330, 1838, 10758, 65586, 413639, 2684469, 17852715, 121256457, 838843641, 5897455515, 42058344077, 303787163823, 2219452035639, 16383022072549, 122066094872139, 917245868993865, 6946236553301334, 52979616083094066, 406741647662973594
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) ~ 4 * 3^(2*n+1/2) / (Pi*n^4). - Vaclav Kotesovec, Apr 02 2017
MATHEMATICA
Rest[CoefficientList[Series[2*x - 1 + (1-x)^2 * (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), {x, 0, 30}], x]] (* Vaclav Kotesovec, Apr 02 2017 *)
CROSSREFS
Sequence in context: A193112 A367061 A192729 * A107097 A202837 A370396
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Apr 02 2017
EXTENSIONS
More terms from Vaclav Kotesovec, Apr 02 2017
STATUS
approved