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

Author

N. J. A. Sloane, Dec 22 2012

Keywords

• nonn

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.

Crossrefs

Column 3 of A339650.

Cf. A129860, A220826, A220827, A220829.

Formula

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

Extensions

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