A161746 The number of equivalence classes of n-leaf binary trees with respect to contiguous pattern avoidance.

1, 1, 1, 2, 3, 7, 15, 43, 136

Offset

1,4

Links

Table of n, a(n) for n=1..9.

Andrey T. Cherkasov and Dmitri Piontkovski, Wilf classes of non-symmetric operads, arXiv:2105.08880 [math.CO], 2021.

L. Pudwell, Pattern avoidance in trees, (slides from a talk, mentions many sequences), 2012. - N. J. A. Sloane, Jan 03 2013

Eric S. Rowland, Pattern avoidance in binary trees, arXiv:0809.0488 [math.CO], 2008-2010.

Eric S. Rowland, Pattern avoidance in binary trees, J. Comb. Theory A 117 (6) (2010) 741-758.

Example

Representatives of the a(6) = 7 equivalence classes of 6-leaf binary trees are given in A036766, A159768, A159769, A159770, A159771, A159772, and A159773.

Crossrefs

Cf. A099952.

Sequence in context: A289470 A368564 A213385 * A045629 A034731 A216435

Adjacent sequences: A161743 A161744 A161745 * A161747 A161748 A161749

Keyword

nonn,hard,more

Author

Eric Rowland, Jun 17 2009

Extensions

Per Cherkasov and Piontkovski, a(8) corrected by Eric Rowland, May 22 2021

a(9) from Eric Rowland, Apr 25 2024

Status

approved