A220830 Number of unrooted binary leaf-multi-labeled trees with n leaves on the label set [3], with each label used at least once.

0, 0, 1, 6, 30, 140, 663, 3186, 15642, 78441, 400842, 2084698, 11009358, 58955139, 319619706, 1752122667, 9700923252, 54194387085, 305216395077, 1731579241287, 9889280682948, 56822058078669, 328300135291659, 1906449141877331, 11122447670117451, 65168427936552522

Offset

1,4

Links

Andrew Howroyd, Table of n, a(n) for n = 1..200

V. P. Johnson, Enumeration Results on Leaf Labeled Trees, Ph. D. Dissertation, Univ. Southern Calif., 2012.

Formula

a(n) = A220827(n) - 3*A220826(n) + 3*A129860(n). - Andrew Howroyd, Dec 14 2020

Crossrefs

Column 3 of A339650.

Cf. A129860, A220826, A220827, A220829.

Sequence in context: A082149 A002457 A137400 * A199938 A285195 A307321

Adjacent sequences: A220827 A220828 A220829 * A220831 A220832 A220833

Keyword

nonn

Author

N. J. A. Sloane, Dec 22 2012

Extensions

Terms a(11) and beyond from Andrew Howroyd, Dec 14 2020

Status

approved