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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.

S. M. Gusein-Zade and F. S. Duzhin, Enumeration of plane curves with up to 10 selfintersections, Pascal program and result table, 05 Apr 1998.

PROG

(Pascal) Cf. link.

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,more

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 June 4 01:54 EDT 2020. Contains 334812 sequences. (Running on oeis4.)