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A004300
Number of symmetric irreducible diagrams with 2n nodes.
(Formerly M1758)
3
1, 1, 2, 7, 22, 96, 380, 1853, 8510, 44940, 229836, 1296410, 7211116, 43096912, 256874200, 1617413773, 10226972110, 67542201972, 449809389740, 3104409032126
OFFSET
1,3
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
Jonathan Burns, Egor Dolzhenko, Natasa Jonoska, Tilahun Muche, and Masahico Saito, Four-Regular Graphs with Rigid Vertices Associated to DNA Recombination, Discrete Applied Mathematics, Volume 161, Issues 10-11, July 2013, Pages 1378-1394; and preprint, 2011.
Jonathan Burns and Tilahun Muche, Counting Irreducible Double Occurrence Words, arXiv preprint arXiv:1105.2926 [math.CO], 2011.
Martin Klazar, Non-P-recursiveness of numbers of matchings or linear chord diagrams with many crossings, Advances in Appl. Math., Vol. 30 (2003), pp. 126-136.
Paul R. Stein, On a class of linked diagrams, I. Enumeration, J. Combin. Theory, A 24 (1978), 357-366.
Paul R. Stein and C. J. Everett, On a class of linked diagrams, II. Asymptotics, Discrete Math., 21 (1978), 309-318.
CROSSREFS
Cf. A000699.
Sequence in context: A150333 A057787 A217138 * A049369 A327697 A308548
KEYWORD
nonn,nice,easy
STATUS
approved