

A202037


Number of unlabeled 6trees on n nodes


2



0, 0, 0, 0, 0, 1, 1, 1, 2, 5, 15, 64, 342, 2344, 19090, 179562, 1878277, 21365403, 258965451, 3294561195, 43472906719, 589744428065, 8171396893523, 115094557122380, 1642269376265063, 23679803216530017, 344396036645439675, 5045351124912000756
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OFFSET

1,9


COMMENTS

A ktree is recursively defined as follows: K_k is a ktree and any ktree on n+1 vertices is obtained by joining a vertex to a kclique in a ktree on n vertices.


REFERENCES

Miklos Bona, editor, Handbook of Enumerative Combinatorics, CRC Press, 2015, page 328.


LINKS

Table of n, a(n) for n=1..28.
Andrew GainerDewar, GammaSpecies and the Enumeration of kTrees, Electronic Journal of Combinatorics, Volume 19 (2012), #P45.  From N. J. A. Sloane, Dec 15 2012


CROSSREFS

Cf. A054581 (unlabeled 2trees), A078792 (unlabeled 3trees), A078793 (unlabeled 4trees), A201702 (unlabeled 5trees)
Sequence in context: A130756 A078793 A201702 * A322754 A224917 A274100
Adjacent sequences: A202034 A202035 A202036 * A202038 A202039 A202040


KEYWORD

nonn


AUTHOR

Andrew R. Gainer, Dec 09 2011


STATUS

approved



