OFFSET
0,2
COMMENTS
a(n) is the number of multigraphs with 2n unlabeled nodes of degree 3 plus 2 noninterchangeable nodes of degree 1, loops allowed. - Andrew Howroyd, Mar 10 2023
LINKS
R. de Mello Koch and S. Ramgoolam, Strings from Feynman graph counting: Without large N, Phys. Rev. D 85 (2012) 026007, App. D.
R. J. Mathar, Illustrations
CROSSREFS
KEYWORD
nonn
AUTHOR
R. J. Mathar, Mar 07 2022
EXTENSIONS
a(0) prepended and terms a(9) and beyond from Andrew Howroyd, Mar 10 2023
STATUS
approved