A268565 Number of achiral immersions of oriented circle into oriented sphere with 2n double points.

1, 1, 5, 15, 97, 592, 4488, 35314, 295379

Offset: 0

Author

N. J. A. Sloane, Mar 03 2016

Keywords

• nonn
• more

Links

• Robert Coquereaux and Jean-Bernard Zuber, Maps, immersions and permutations, Journal of Knot Theory and Its Ramifications, Vol. 25, No. 8 (2016), 1650047; arXiv preprint, arXiv:1507.03163 [math.CO], 2015-2016. See Eq. (17), r_m.

Crossrefs

Cf. A008986, A008987, A268566.

Formula

a(n) = 2 * A008988(2*n) - A008986(2*n). - Andrey Zabolotskiy, Jun 05 2024

Extensions

Name clarified and a(0), a(6)-a(8) added using formula by Andrey Zabolotskiy, Jun 08 2024