|
|
A243013
|
|
Number of graphs with n vertices and n-1 edges that can be gracefully labeled.
|
|
0
|
|
|
|
OFFSET
|
1,4
|
|
COMMENTS
|
Hand calculated by grade 3 students up to term 6: (1,1,1,3,5,12...)
|
|
LINKS
|
|
|
EXAMPLE
|
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.
|
|
KEYWORD
|
more,nonn
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|