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%I #25 Mar 30 2024 21:20:09
%S 1,2,5,20,82,435,2645,18489,141326,1153052,9819315,86305315,776868505
%N Number of immersions of the unoriented circle into the unoriented plane with n double points.
%D V. I. Arnold, Topological Invariants of Plane Curves and Caustics, American Math. Soc., 1994, p. 16.
%H S. R. Finch, <a href="http://www.people.fas.harvard.edu/~sfinch/">Knots, links and tangles</a>
%H S. R. Finch, <a href="/A002863/a002863_4.pdf">Knots, links and tangles</a>, Aug 08 2003. [Cached copy, with permission of the author]
%H S. M. Gusein-Zade and F. S. Duzhin, <a href="https://doi.org/10.4213/rm48">On the number of topological types of plane curves</a> (Russian), Uspekhi Mat. Nauk 53 (1998), no. 3(321), 197-198. <a href="https://doi.org/10.1070/RM1998v053n03ABEH000048">English translation</a>: Russian Mathematical Surveys 53 (1998) 626-627. <a href="https://www.pdmi.ras.ru/~arnsem/dataprog/">Related program and data</a>.
%Y Cf. A008980, A008981, A008982, A008984, A008985, A054993.
%Y Cf. A008989 (immersions into sphere), A118814 (tree-like immersions).
%K nonn,nice,more
%O 0,2
%A _N. J. A. Sloane_
%E Additional comments from _Sergei Duzhin_, Nov 11 2000
%E a(11)-a(12) from _Sean A. Irvine_, Apr 19 2018
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