

A258489


Number of tangled chains of length k=6.


8



1, 1, 122, 474883, 11168414844, 989169269347359, 250335000079534559375, 151038989624520433840089358, 191158216491241179675824199407135, 461408865973380293005829125668717407727, 1973397409908124305318632313047269426852165625, 14104214451439837037643144221899175649593123932192274
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OFFSET

1,3


COMMENTS

Tangled chains are ordered lists of k rooted binary trees with n leaves and a matching between each leaf from the ith tree with a unique leaf from the (i+1)st tree up to isomorphism on the binary trees. This sequence fixes k=6, and n = 1,2,3,...


REFERENCES

R. Page, Tangled trees: phylogeny, cospeciation, and coevolution, The University of Chicago Press, 2002.


LINKS

Table of n, a(n) for n=1..12.
Sara Billey, Matjaž Konvalinka, and Frederick A. Matsen IV, On the enumeration of tanglegrams and tangled chains, arXiv:1507.04976 [math.CO], 2015.


FORMULA

t(n) = Sum_{b=(b(1),...,b(t))} Product_{i=2..t} (2(b(i)+...+b(t))1)^6)/z(b) where the sum is over all binary partitions of n and z(b) is the size of the stabilizer of a permutation of cycle type b under conjugation.


CROSSREFS

Cf. A000123 (binary partitions), A258620 (tanglegrams), A258485, A258486, A258487, A258488, A258489 (tangled chains), A259114 (unordered tanglegrams).
Sequence in context: A098129 A198603 A237640 * A015079 A015042 A062233
Adjacent sequences: A258486 A258487 A258488 * A258490 A258491 A258492


KEYWORD

nonn


AUTHOR

Sara Billey, Matjaz Konvalinka, and Frederick A. Matsen IV, May 31 2015


STATUS

approved



