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A008980 Number of immersions of the oriented circle into the oriented plane with n double points. 6
2, 3, 10, 39, 204, 1262, 8984, 67959, 544504, 4535030, 39004772, 344217402, 3103896536 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,1

REFERENCES

V. I. Arnold, Topological Invariants of Plane Curves and Caustics, American Math. Soc., 1994, p. 16.

LINKS

Table of n, a(n) for n=0..12.

S. M. Gusein-Zade and F. S. Duzhin, On the number of topological types of plane curves; (Russian) Uspekhi Mat. Nauk 53 (1998), no. 3(321), 197-198. English translation: Russian Mathematical Surveys 53 (1998) 626-627.

CROSSREFS

Cf. A008981, A008982, A008983, A008984, A008985, A054993.

Sequence in context: A144720 A164933 A003048 * A064183 A050381 A129716

Adjacent sequences:  A008977 A008978 A008979 * A008981 A008982 A008983

KEYWORD

nonn,nice

AUTHOR

N. J. A. Sloane

EXTENSIONS

Additional comments from Sergei Duzhin, Nov 11 2000

a(11)-a(12) from Sean A. Irvine, Apr 19 2018

STATUS

approved

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Last modified November 14 06:49 EST 2018. Contains 317162 sequences. (Running on oeis4.)