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

1,3

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.

Formula

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

Prog

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

Crossrefs

Column 2 of A339650.

Cf. A129860, A220826.

Sequence in context: A113066 A002459 A216434 * A339838 A104383 A205480

Adjacent sequences: A220826 A220827 A220828 * A220830 A220831 A220832

Keyword

nonn

Author

N. J. A. Sloane, Dec 22 2012

Extensions

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

Status

approved