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%I #17 Dec 15 2020 12:54:22
%S 2,3,4,6,12,31,78,234,722,2376,8046,28263,101226,370389,1375728,
%T 5182107,19743204,75994993,295110996,1155128397,4553360558,
%U 18063221619,72069527418,289053637621,1164871141254,4714973350560,19161577759814,78162897838290,319940064689142
%N Number of unrooted binary leaf-multi-labeled trees with n leaves on the label set [2].
%H Andrew Howroyd, <a href="/A220826/b220826.txt">Table of n, a(n) for n = 1..500</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.
%o (PARI) U(30,2) \\ See A339649 for U(n,k). - _Andrew Howroyd_, Dec 14 2020
%Y Column 2 of A339649.
%Y Cf. A083563, A220829.
%K nonn
%O 1,1
%A _N. J. A. Sloane_, Dec 22 2012
%E Terms a(11) and beyond from _Andrew Howroyd_, Dec 14 2020
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