A263866 - OEIS

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A263866

Number of permutations of [n] with no carrier element, that is, having their exterior (longest pattern that is both a proper prefix and a proper suffix) contained in their interior (permutation obtained by deleting the first and the last entry) as a consecutive pattern.

0, 4, 12, 84, 548, 4172, 33984, 315800, 3213032

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OFFSET

2,2

LINKS

Table of n, a(n) for n=2..10.

Antonio Bernini, Luca Ferrari, and Einar Steingrímsson, The Möbius function of the consecutive pattern poset, Electron. J. Combin., 18(1):Paper 146, 12 pp., 2011.

Sergi Elizalde, Peter R. W. McNamara, The structure of the consecutive pattern poset, arXiv:1508.05963 [math.CO], 2015.

Bruce E. Sagan and Robert Willenbring, Discrete Morse theory and the consecutive pattern poset, J. Algebraic Combin., 36(4):501-514, 2012.

EXAMPLE

For n=3, we have a(3)=4 because the permutations 132, 213, 231, 312 have exterior equal to 1, and thus contained in their interior. On the other hand, 123 has exterior 12, and 321 has exterior 21.

CROSSREFS

Sequence in context: A305334 A205337 A359047 * A208802 A226960 A081214

Adjacent sequences: A263863 A263864 A263865 * A263867 A263868 A263869

KEYWORD

nonn,more

AUTHOR

Sergi Elizalde, Oct 28 2015

STATUS

approved