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Search: id:A000675
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| A000675 |
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Number of centered 3-valent (or boron, or binary) trees with n nodes.
(Formerly M0977 N0366)
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+0
3
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| 1, 1, 0, 1, 1, 1, 2, 4, 5, 10, 19, 36, 68, 138, 277, 581, 1218, 2591, 5545, 12026, 26226, 57719, 127685, 284109, 634919, 1425516, 3212890, 7269605, 16504439, 37592604, 85876345, 196717882, 451768247, 1039990913, 2399476030, 5547849750
(list; graph; listen)
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OFFSET
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0,7
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
A. Cayley, On the analytical forms called trees, with application to the theory of chemical combinations, Reports British Assoc. Advance. Sci. 45 (1875), 257-305 = Math. Papers, Vol. 9, 427-460 (see p. 451).
R. C. Read, personal communication.
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LINKS
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E. M. Rains and N. J. A. Sloane, On Cayley's Enumeration of Alkanes (or 4-Valent Trees)., J. Integer Sequences, Vol. 2 (1999), Article 99.1.1.
Index entries for sequences related to trees
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CROSSREFS
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A000672 = A000673 + A000675. Cf. A000022, A000200, A000602.
Sequence in context: A046430 A133040 A018424 this_sequence A005018 A118551 A161706
Adjacent sequences: A000672 A000673 A000674 this_sequence A000676 A000677 A000678
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KEYWORD
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nonn,easy,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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