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A008986
Number of immersions of oriented circle into oriented sphere with n double points.
15
1, 1, 3, 9, 37, 182, 1143, 7553, 54559, 412306, 3251240, 26478264, 221714164, 1900103364, 16613990484, 147816411921, 1335367515821
OFFSET
0,3
COMMENTS
a(10) = 3251240 by sampling method (to be confirmed, cf. ref. arXiv:1507.03163). - Robert Coquereaux, Nov 23 2015
a(10) = 3251240 confirmed. - Brendan McKay, Mar 29 2024
REFERENCES
V. I. Arnold, Topological Invariants of Plane Curves and Caustics, American Math. Soc., 1994, p. 18.
LINKS
R. Coquereaux and J.-B. Zuber, Maps, immersions and permutations, arXiv preprint arXiv:1507.03163 [math.CO], 2015-2016. Also J. Knot Theory Ramifications 25, 1650047 (2016), DOI: http://dx.doi.org/10.1142/S0218216516500474
Guy Valette, A Classification of Spherical Curves Based on Gauss Diagrams, Arnold Math J. (2016) 2:383-405.
PROG
(Magma) /* For Magma program see A260285. */
CROSSREFS
Cf. A008987, A008988, A008989. First line of triangle A260285.
Sequence in context: A319119 A006229 A321734 * A105215 A158053 A009179
KEYWORD
nonn,more
EXTENSIONS
a(6)-a(7) from Guy Valette, Feb 09 2004
a(8)-a(9) from Robert Coquereaux and Jean-Bernard Zuber, Jul 21 2015
a(10) from same source added by N. J. A. Sloane, Mar 03 2016
a(11)-a(16) from Brendan McKay, Mar 29 2024
STATUS
approved