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A373721
Number of trees with n nodes which have nodes that cannot be gracefully labeled '0'.
0
0, 0, 0, 0, 0, 0, 1, 1, 3, 3, 4, 5, 9, 9, 14
OFFSET
0,9
COMMENTS
Also called non-0-ubiquitous.
LINKS
Frank Van Bussel, 0-Centred and 0-ubiquitously graceful trees, Discrete Mathematics 277.1-3 (2004): 193-218. See Section 2.
EXAMPLE
For n=6 the tree with a-b-c-d-e
\
f
has no graceful solution with 'c' labeled as '0'.
CROSSREFS
Sequence in context: A241442 A378750 A363091 * A043551 A162888 A337402
KEYWORD
nonn,more
AUTHOR
Michael Arnold, Jun 15 2024
STATUS
approved