A220829 Number of unrooted binary leaf-multi-labeled trees with n leaves on the label set [2], with each label used at least once.

0, 1, 2, 4, 10, 27, 74, 226, 710, 2354, 8010, 28189, 101094, 370119, 1375198, 5181003, 19740940, 75990173, 295100800, 1155106357, 4553312866, 18063117153, 72069297826, 289053128879, 1164870009786, 4714970819402, 19161572076550, 78162885020942, 319940035684684, 1313799822309748

Offset: 1

Author

N. J. A. Sloane, Dec 22 2012

Keywords

• nonn

Links

• Andrew Howroyd, Table of n, a(n) for n = 1..500
• V. P. Johnson, Enumeration Results on Leaf Labeled Trees, Ph. D. Dissertation, Univ. Southern Calif., 2012.

Crossrefs

Column 2 of A339650.

Cf. A129860, A220826.

Programs

PARI

my(N=30); U(N,2) - 2*U(N,1) \\ See A339650 for U(n,k). - Andrew Howroyd, Dec 14 2020

Formula

a(n) = A220826(n) - 2*A129860(n). - Andrew Howroyd, Dec 14 2020

Extensions

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