7 Feb
2007
7 Feb
'07
1:02 a.m.
On 2/6/07, Mike Speciner <speciner@ll.mit.edu> wrote:
Aren't there 5 for n=5?
I, L, N, W, V, U, and Z all are isomorphic graphs (5 vertices in a line, degrees 1,2,2,2,1) F, T, and Y are four in a line with a branch of the side, degrees 1,2,3,1,1 P has four in a block with one off the side, degrees 2,2,2,3,1 And then there's X, with degrees 4,1,1,1,1 I know the degrees of the vertices isn't enough to prove the graphs isomorphic in general but in this case I think it's true that all the pentominoes with the same list of degrees are indeed isomorphic. So I get 4 ... --Joshua Zucker