A008982 Number of immersions of the oriented circle into the unoriented plane with n double points.

1, 2, 5, 21, 102, 640, 4492, 34047, 272252, 2268085, 19502386, 172113886, 1551948268

Offset: 0

Author

N. J. A. Sloane

Keywords

• nonn
• nice

References

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

Links

• 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.

Crossrefs

Cf. A008980, A008981, A008983, A008984, A008985, A054993.

Extensions

Additional comments from Sergei Duzhin, Nov 11 2000

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