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A259116 Number of unrooted binary unordered tanglegrams of size n. 2
1, 1, 1, 2, 4, 22, 145, 1875, 31929, 698183, 18056523, 538340256, 18141423039, 681939320185 (list; graph; refs; listen; history; text; internal format)



Binary tanglegrams are pairs of bifurcating (degree 3 internal node) trees with a bijection between the leaves of the trees. Two tanglegrams are isomorphic if there is an isomorphism between the trees that preserves the bijection. Unrooted means that the tanglegram is composed of unrooted trees, and unordered means that two tanglegrams that differ by exchanging the trees and inverting the bijection are considered identical.


Table of n, a(n) for n=1..14.

S. C. Billey, M. Konvalinka, and F. A. Matsen IV, On the enumeration of tanglegrams and tangled chains, arXiv:1507.04976 [math.CO], 2015.

Ira M. Gessel, Counting tanglegrams with species, arXiv:1509.03867 [math.CO], (13-September-2015)

F. A. Matsen IV, S. C. Billey, D. A. Kas, and M. Konvalinka, Tanglegrams: a reduction tool for mathematical phylogenetics, arXiv:1507.04784 [q-bio.PE], 2015.

Frederick A. Matsen, Sage/GAP4 Code for generating tanglegrams


Cf. A258620 (tanglegrams), A259114, A259115, A258486 (tangled chains), A258487, A258488, A258489.

Sequence in context: A321248 A309741 A110130 * A283322 A019025 A264729

Adjacent sequences:  A259113 A259114 A259115 * A259117 A259118 A259119




Frederick A. Matsen IV, Jun 18 2015


More terms from Ira M. Gessel, Jul 19 2015



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