

A008986


Number of immersions of oriented circle into oriented sphere with n double points.


9



1, 1, 3, 9, 37, 182, 1143, 7553, 54559, 412306, 3251240
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OFFSET

0,3


COMMENTS

a(10) = 3521240 by sampling method (to be confirmed, cf. ref. arXiv:1507.03163).  Robert Coquereaux, Nov 23 2015


REFERENCES

V. I. Arnold, Topological Invariants of Plane Curves and Caustics, American Math. Soc., 1994, p. 18.
Guy Valette, A Classification of Spherical Curves Based on Gauss Diagrams, Arnold Math J. (2016) 2:383405, DOI 10.1007/s4059801600493.


LINKS

Table of n, a(n) for n=0..10.
R. Coquereaux, J.B. Zuber, Maps, immersions and permutations, arXiv preprint arXiv:1507.03163 [math.CO], 2015. Also J. Knot Theory Ramifications 25, 1650047 (2016), DOI: http://dx.doi.org/10.1142/S0218216516500474


PROG

For Magma program see A260285.


CROSSREFS

Cf. A008987, A008988, A008989. First line of triangle A260285.
Sequence in context: A319119 A006229 A321734 * A105215 A158053 A009179
Adjacent sequences: A008983 A008984 A008985 * A008987 A008988 A008989


KEYWORD

nonn,more


AUTHOR

N. J. A. Sloane


EXTENSIONS

a(6)a(7) from Guy Valette, Feb 09 2004
a(8)a(9) from Robert Coquereaux and JeanBernard Zuber, Jul 21 2015
a(10) from same source added by N. J. A. Sloane, Mar 03 2016


STATUS

approved



