A284719 Number of indecomposable permutations avoiding the pattern 1234.

1, 1, 3, 13, 69, 400, 2390, 14545, 90285, 572801, 3715919, 24627773, 166497633, 1146141359, 8019377521, 56936916951, 409590294555, 2981507133559, 21935750057293, 162953508604187, 1221207542430487, 9225662325264922, 70209599158600184, 537934680500809021

Offset

1,3

Links

Table of n, a(n) for n=1..24.

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 * A379090 A128079 A074534

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