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A323389 The number of connected, unlabeled, undirected, edge-signed cubic graphs (admitting loops and multiedges) on 2n vertices where the degree of the first sign is 2 at each node. 0
1, 2, 5, 19, 88, 553 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Obtained from the cubic graphs A005967 (connected undirected cubic graphs that may have loops and/or multiedges) by signing each edge with a plus or a minus such that two pluses and one minus meet at each vertex.

LINKS

Table of n, a(n) for n=0..5.

Richard J. Mathar, Feynman diagrams of the QED vacuum polarization, vixra:1901.0148 (2019) Section II.

CROSSREFS

Cf. A005967 (unsigned), A054499 (only one cycle of pluses), A170946 (directed plus-edges).

Sequence in context: A326563 A316700 A124348 * A268605 A205804 A052324

Adjacent sequences:  A323386 A323387 A323388 * A323390 A323391 A323392

KEYWORD

nonn,more

AUTHOR

R. J. Mathar, Jan 13 2019

STATUS

approved

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Last modified September 18 19:30 EDT 2021. Contains 347534 sequences. (Running on oeis4.)