A220826 Number of unrooted binary leaf-multi-labeled trees with n leaves on the label set [2].

2, 3, 4, 6, 12, 31, 78, 234, 722, 2376, 8046, 28263, 101226, 370389, 1375728, 5182107, 19743204, 75994993, 295110996, 1155128397, 4553360558, 18063221619, 72069527418, 289053637621, 1164871141254, 4714973350560, 19161577759814, 78162897838290, 319940064689142

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 A339649.

Cf. A083563, A220829.

Programs

PARI

U(30,2) \\ See A339649 for U(n,k). - Andrew Howroyd, Dec 14 2020

Extensions

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