OFFSET
1,3
COMMENTS
Also, bipartite cubic multigraphs up to color-preserving isomorphism, with no edges of multiplicity 3.
EXAMPLE
For n=3 the a(3)=3 solutions are [2,1,0; 1,0,2; 0,2,1], [1,1,1; 2,0,1; 0,2,1] and [1,1,1; 1,1,1; 1,1,1].
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
Brendan McKay, Oct 05 2019
EXTENSIONS
a(13) corrected and terms a(14) and beyond from Andrew Howroyd, Apr 11 2020
STATUS
approved