A278994 - OEIS

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A278994

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

3

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

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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