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Search: id:A008981
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| A008981 |
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Number of immersions of the unoriented circle into the oriented plane with n double points. |
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+0
7
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| 1, 2, 5, 21, 102, 639, 4492, 34032, 272252, 2267905, 19502386
(list; graph; listen)
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OFFSET
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0,2
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REFERENCES
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V. I. Arnold, Topological Invariants of Plane Curves..., American Math. Soc., 1994, p. 16.
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LINKS
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S. M. Gusein-Zade and F. S. Duzhin, On the number of topological types of plane curves; (Russian) Uspekhi Mat. Nauk 53 (1998), number 3(321), 197-198. English translation: Russian Mathematical Surveys 53 (1998) 626-627.
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CROSSREFS
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Cf. A008980, A008982, A008983, A008984, A008985, A054993.
Sequence in context: A062297 A047104 A115087 this_sequence A008982 A130471 A002628
Adjacent sequences: A008978 A008979 A008980 this_sequence A008982 A008983 A008984
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KEYWORD
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nonn,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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Additional comments from Sergei V. Duzhin (duzhin(AT)botik.ru), Nov 11, 2000.
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