A243391 - OEIS

A243391

Number of isomorphism classes of connected 3-regular loopless multigraphs with n vertices and with semi-edges allowed.

1, 3, 4, 12, 22, 68, 166, 534, 1589, 5464, 18579, 68320, 255424, 1000852, 4018156, 16671976, 70890940, 309439942, 1381815168, 6310880471, 29428287639, 140012980007, 678970863717, 3353545264060, 16857749613964, 86191265140699, 447951112379963, 2365177154077186

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OFFSET

1,2

COMMENTS

a(n) is also the number of isomorphism classes of connected loopless multigraphs with n vertices of degree 3 or less. - Andrew Howroyd, Mar 20 2020

LINKS

Table of n, a(n) for n=1..28.

G. Brinkmann, N. Van Cleemput, T.Pisanski, Generation of various classes of trivalent graphs, Theoretical Computer Science 502, 2013, pp.16-29.

CROSSREFS

Column k=3 of A334546.

Cf. A000421, A243392, A243393, A243394, A303030.

Sequence in context: A295948 A129922 A005221 * A000206 A368031 A240737