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Number of unrooted binary leaf-multi-labeled trees with n leaves on the label set [3], with each label used at least once.
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%I #17 Dec 15 2020 12:52:25

%S 0,0,1,6,30,140,663,3186,15642,78441,400842,2084698,11009358,58955139,

%T 319619706,1752122667,9700923252,54194387085,305216395077,

%U 1731579241287,9889280682948,56822058078669,328300135291659,1906449141877331,11122447670117451,65168427936552522

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

%H Andrew Howroyd, <a href="/A220830/b220830.txt">Table of n, a(n) for n = 1..200</a>

%H V. P. Johnson, <a href="https://people.math.sc.edu/czabarka/Theses/JohnsonThesis.pdf">Enumeration Results on Leaf Labeled Trees</a>, Ph. D. Dissertation, Univ. Southern Calif., 2012.

%F a(n) = A220827(n) - 3*A220826(n) + 3*A129860(n). - _Andrew Howroyd_, Dec 14 2020

%Y Column 3 of A339650.

%Y Cf. A129860, A220826, A220827, A220829.

%K nonn

%O 1,4

%A _N. J. A. Sloane_, Dec 22 2012

%E Terms a(11) and beyond from _Andrew Howroyd_, Dec 14 2020