A278994 Number of simple chord diagrams with n chords, modulo all symmetries.

0, 1, 1, 4, 18, 116, 1060, 13019, 193425, 3313522, 63667788, 1351700744, 31390695708, 791372281393, 21523271532811, 628166776833181, 19582955637428422, 649472761243051940, 22833268501579122332, 848230375982060558217

Offset

1,4

Links

Table of n, a(n) for n=1..20.

E. Krasko and A. Omelchenko, Enumeration of Chord Diagrams without Loops and Parallel Chords, arXiv preprint arXiv:1601.05073 [math.CO], 2016.

E. Krasko and A. Omelchenko, Enumeration of Chord Diagrams without Loops and Parallel Chords, The Electronic Journal of Combinatorics, 24(3) (2017), #P3.43.

Crossrefs

Cf. A003436, A003437, A007474, A278990, A278991, A278992, A278993.

Sequence in context: A137567 A326261 A277473 * A223008 A162224 A321704

Adjacent sequences: A278991 A278992 A278993 * A278995 A278996 A278997

Keyword

nonn

Author

N. J. A. Sloane, Dec 07 2016

Status

approved