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

0,3

Links

Table of n, a(n) for n=0..8.

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.

Formula

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

Crossrefs

Cf. A008986, A008987, A268566.

Sequence in context: A134135 A292279 A381064 * A358197 A121869 A118412

Adjacent sequences: A268562 A268563 A268564 * A268566 A268567 A268568

Keyword

nonn,more

Author

N. J. A. Sloane, Mar 03 2016

Extensions

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

Status

approved