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A111299
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Numbers n such that the Matula tree of n is a binary tree (i.e. all nodes except root and leaves have degree 3).
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0
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4, 14, 49, 86, 301, 454, 886, 1589, 1849, 3101, 3986, 6418, 9761, 13766, 13951, 19049, 22463, 26798, 31754, 48181, 51529, 57026, 75266, 85699, 93793, 100561
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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REFERENCES
| F. Goebel, On a 1-1-correspondence between rooted trees and natural numbers, J. Combin. Theory, B 29 (1980), 141-143. D. Matula, A natural rooted tree enumeration by prime factorization, SIAM Rev. 10 (1968).
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LINKS
| Keith Briggs, Matula numbers and rooted trees
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FORMULA
| The Matula tree of n is defined by as follows (p_m denotes the m-th prime):
matula(n):
... create a node labeled n
... for each prime factor m of n:
...... add the subtree matula(p_m), by an edge labeled m
... return the node
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CROSSREFS
| Cf. A061773, A005517, A005518.
Sequence in context: A014325 A047028 A047138 * A110686 A071729 A071733
Adjacent sequences: A111296 A111297 A111298 * A111300 A111301 A111302
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KEYWORD
| nonn
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AUTHOR
| Keith Briggs (keith.briggs(AT)bt.com), Nov 02 2005
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