A264761 Number of irreducible indecomposable spherical curves with n crossings (only ordinary double points), the circle is oriented, the sphere is oriented (OO case).

0, 0, 1, 1, 2, 6, 17, 73, 290, 1274, 5844, 27750, 135192, 676263, 3437509, 17811771, 93531354, 497835030, 2680058068, 14577839412, 80039070868, 443164758244, 2472713506356

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 distinct lines.

Links

Table of n, a(n) for n=1..23.

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: 10.1142/S0218216516500474.

Prog

(C) See the J. Betrema C program in the Tait Curves link.

Crossrefs

Cf. A008986, A008987, A008988, A008989, A007756, A264759, A264760.

Sequence in context: A150040 A346043 A079456 * A253882 A327698 A183757

Adjacent sequences: A264758 A264759 A264760 * A264762 A264763 A264764

Keyword

nonn,more

Author

Robert Coquereaux, Nov 23 2015

Extensions

a(15)-a(16) using J. Betrema's program added by Andrey Zabolotskiy, Aug 24 2023

a(17)-a(23) from Brendan McKay, Mar 30 2024

Status

approved