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A118814 Number of 'tree-like curves' with n intersection points, useing the definition in V. I. Arnold's "Topological Invariants of plane curves and caustics", page 12. +0
1
1, 2, 5, 18, 70 (list; graph; listen)
OFFSET

0,2

COMMENT

The objects being enumerated are a subset of those enumerated by A008983. The restriction involved is that the gauss diagram (or chord diagram)has no intersecting chords. The first 3 entries are the same as A008983 because, for less than 3 intersection points, all curves are tree-like. For 3 intersection points there are only 2 curves that are not tree-like. They appear as the 4th and 15th entries in the table for n=3, on page 14 of Arnold's book. ( For all I know, this sequence may be equal to one of the others allready in the database with the same initial terms.)

CROSSREFS

Cf. A008983.

Sequence in context: A150023 A150024 A150025 this_sequence A014271 A073157 A141494

Adjacent sequences: A118811 A118812 A118813 this_sequence A118815 A118816 A118817

KEYWORD

nonn

AUTHOR

Moshe Newman (mshnoiman(AT)gmail.com), May 23 2006

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Last modified December 15 00:47 EST 2009. Contains 170825 sequences.


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