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A220826
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Number of unrooted binary leaf-multi-labeled trees with n leaves on the label set [2].
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4
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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
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OFFSET
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1,1
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LINKS
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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.
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PROG
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(PARI) U(30, 2) \\ See A339649 for U(n, k). - Andrew Howroyd, Dec 14 2020
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CROSSREFS
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Column 2 of A339649.
Cf. A083563, A220829.
Sequence in context: A275448 A018405 A018419 * A095938 A018460 A018484
Adjacent sequences: A220823 A220824 A220825 * A220827 A220828 A220829
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KEYWORD
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nonn
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AUTHOR
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N. J. A. Sloane, Dec 22 2012
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EXTENSIONS
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Terms a(11) and beyond from Andrew Howroyd, Dec 14 2020
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STATUS
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approved
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