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Number of unlabeled nonseparable (or 2-connected) multigraphs with n edges and degree >= 3 at each node, loops allowed.
2

%I #7 Feb 25 2023 18:07:12

%S 0,0,2,4,9,20,44,113,329,1044,3622,13544,53596,223084,969158

%N Number of unlabeled nonseparable (or 2-connected) multigraphs with n edges and degree >= 3 at each node, loops allowed.

%C A single-edge is considered to be nonseparable here.

%e The a(3) = 2 multigraphs are:

%e - a triple edge;

%e - a single edge with a loop at each vertex.

%Y Row sums of A360870.

%Y Cf. A002935, A360863, A360867.

%K nonn,more

%O 1,3

%A _Andrew Howroyd_, Feb 25 2023