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A220826
Number of unrooted binary leaf-multi-labeled trees with n leaves on the label set [2].
4
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
1,1
LINKS
V. P. Johnson, Enumeration Results on Leaf Labeled Trees, Ph. D. Dissertation, Univ. Southern Calif., 2012.
PROG
(PARI) U(30, 2) \\ See A339649 for U(n, k). - Andrew Howroyd, Dec 14 2020
CROSSREFS
Column 2 of A339649.
Sequence in context: A275448 A018405 A018419 * A095938 A018460 A344661
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Dec 22 2012
EXTENSIONS
Terms a(11) and beyond from Andrew Howroyd, Dec 14 2020
STATUS
approved