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A008982
Number of immersions of the oriented circle into the unoriented plane with n double points.
6
1, 2, 5, 21, 102, 640, 4492, 34047, 272252, 2268085, 19502386, 172113886, 1551948268
OFFSET
0,2
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
KEYWORD
nonn,nice
EXTENSIONS
Additional comments from Sergei Duzhin, Nov 11 2000
a(11)-a(12) from Sean A. Irvine, Apr 19 2018
STATUS
approved