Formula for the number of cubic graphs Cubic graphs form an interesting class of graphs. The are plenty of computational problems that remain NP-complete on this class. Examples include Hamiltonian cycle problem and maximum independent set.
I am interested in the number of cubic graphs on $n$ nodes. 

Is there a closed form formula for the number of cubic graphs? Is there a closed form formula for the number of cubic planar bipartite graphs?

If no such formula exist, What are the best known asymptotic lower bounds?

I agree with the comment above that there is apparently no formula for the number
of cubic graphs. There is some asymptotic information though -
for a start: N. Wormald. Counting labelled 3-connected graphs. J. Graph Theory, 1, 383–384, 1977. There are papers that build on this work.
