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A264760
Number of irreducible indecomposable spherical curves with n crossings (only ordinary double points), the circle is not oriented, the sphere is oriented (UO case).
5
0, 0, 1, 1, 2, 4, 12, 41, 161, 658, 2993, 13974, 67945, 338644, 1720544, 8908579, 46775073, 248932094, 1340079951, 7289000415, 40019815872, 221582832331, 123635832467
OFFSET
1,5
COMMENTS
Irreducible means not made disconnected by removal of a vertex (no nugatory crossings).
Indecomposable (or prime) means not made disconnected by cutting two disjoint lines.
LINKS
J. Betrema, Tait Curves
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
Gunnar Brinkmann and Brendan McKay, plantri plane graph generator. To obtain this sequence use options -Guoqc2m2d (which makes plane quartic graphs) and count those for which the straight-ahead Eulerian walk has a single component.
PROG
(C) See the J. Betrema C program in the Tait Curves link.
KEYWORD
nonn,more
AUTHOR
Robert Coquereaux, Nov 23 2015
EXTENSIONS
a(14)-a(21) from Brendan McKay, Mar 12 2023
plantri link added by Brendan McKay, Mar 25 2024
a(22) and a(23) from Brendan McKay, Mar 30 2024
STATUS
approved