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The number of equivalence classes of n-leaf binary trees with respect to contiguous pattern avoidance.
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%I #29 Apr 26 2024 03:47:50

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

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

%H Andrey T. Cherkasov and Dmitri Piontkovski, <a href="https://arxiv.org/abs/2105.08880">Wilf classes of non-symmetric operads</a>, arXiv:2105.08880 [math.CO], 2021.

%H L. Pudwell, <a href="http://faculty.valpo.edu/lpudwell/slides/notredame.pdf">Pattern avoidance in trees</a>, (slides from a talk, mentions many sequences), 2012. - _N. J. A. Sloane_, Jan 03 2013

%H Eric S. Rowland, <a href="http://arxiv.org/abs/0809.0488">Pattern avoidance in binary trees</a>, arXiv:0809.0488 [math.CO], 2008-2010.

%H Eric S. Rowland, <a href="https://doi.org/10.1016/j.jcta.2010.03.004">Pattern avoidance in binary trees</a>, J. Comb. Theory A 117 (6) (2010) 741-758.

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

%Y Cf. A099952.

%K nonn,hard,more

%O 1,4

%A _Eric Rowland_, Jun 17 2009

%E Per Cherkasov and Piontkovski, a(8) corrected by _Eric Rowland_, May 22 2021

%E a(9) from _Eric Rowland_, Apr 25 2024