Never mind. You're right, there are only 4. --ms Mike Speciner wrote:
Aren't there 5 for n=5?
--ms
Thane Plambeck wrote:
I'm not finding the following sequence in the OEIS, probably because I'm blind to a mistake I've made in counting them.
Consider the set of graphs G(n) constructed in the following way. Take the set of polyominos with n cells. For each polyomino P in turn, put a vertex at the center of each cell, and draw edges between two vertices if they share an edge in the polyomino, obtaining a plain old unidirected graph G with n vertices.
I'm interested in the # of nonisomorphic graphs that are obtained in this way, for each n.
Starting at n=1, I get the sequence
1,1,1,3,4,10
and hits in the OEIS that don't look like they fit for larger n