A243013 Number of graphs with n vertices and n-1 edges that can be gracefully labeled.

1, 1, 1, 3, 5, 12, 36

Offset: 1

Author

Gordon Hamilton, May 28 2014

Keywords

• more
• nonn

Comments

Hand calculated by grade 3 students up to term 6: (1,1,1,3,5,12...)

Examples

			a(5) = 5: A001433 tells us that there are 6 simple graphs with 5 vertices and 4 edges.  Only 5 of these can be labeled gracefully.  The one that cannot is the triangular loop plus two connected nodes: ∆ / .
		

Crossrefs

A001433 provides an upper bound. If the Graceful Tree Conjecture were true, A000055 would be a lower bound.