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Search: id:A131449
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| A131449 |
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Number of organic (also called increasing) vertex labelings of rooted ordered trees with n non-root vertices. |
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+0
1
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| 1, 1, 2, 1, 6, 3, 3, 2, 1, 24, 12, 12, 12, 8, 8, 6, 6, 4, 4, 3, 3, 2, 1, 120, 60, 60, 60, 60, 40, 40, 40, 30, 30, 30, 30, 30, 24, 20, 20, 20, 20, 20, 15, 15, 15, 15, 12, 12, 12, 10, 10, 10, 10, 8, 8, 6, 6, 5, 5, 4, 4, 3, 3, 2, 1, 720
(list; graph; listen)
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OFFSET
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0,3
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COMMENT
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Organic vertex labeling with numbers 1,2,...,n means that the sequence of vertex labels along the (unique) path from the root with label 0 to any leaf (non-root vertex of degree 1) is increasing.
Row lengths sequence, i.e. the number of rooted ordered trees, C(n):=A000108(n) (Catalan numbers): [1,1,2,5,14,42,...].
Number of rooted trees with n non-root vertices [1,1,2,4,9,20,...]=A000081(n+1).
Row sums give [1,1,3,155,105,945,...]= A001147(n), n>=0. A035342(n,1), n>=1, first column of triangle S2(3).
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LINKS
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W. Lang, First 6 rows.
W. Lang, Rooted ordered trees with n=5 non-root vertices and number of labelings.
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EXAMPLE
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[0! ]; [1! ]; [2!,1]; [3!,3,3,2,1], [4!,12,12,12,8,8,6,6,4,4,3,3,2,1];...
n=3: 3 labelings (0,1,2)(0,3), (0,1,3) (0,2) and (0,2,3) (0,1) for the rooted tree o-o-x-o.
n=3: 3 labelings (0,3)(0,1,2), (0,2)(0,1,3) and (0,1)(0,2,3) for the rooted tree o-x-o-o.
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CROSSREFS
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Sequence in context: A094310 A165908 A121281 this_sequence A124443 A077172 A160047
Adjacent sequences: A131446 A131447 A131448 this_sequence A131450 A131451 A131452
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KEYWORD
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nonn,more,tabf
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AUTHOR
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Wolfdieter Lang (wolfdieter.lang(AT)physik.uni-karlsruhe.de) Aug 07 2007
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