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 A243013 Number of graphs with n vertices and n-1 edges that can be gracefully labeled. 0
 1, 1, 1, 3, 5, 12, 36 (list; graph; refs; listen; history; text; internal format)
 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. Sequence in context: A220832 A323270 A087610 * A191636 A267337 A308544 Adjacent sequences:  A243010 A243011 A243012 * A243014 A243015 A243016 KEYWORD more,nonn AUTHOR Gordon Hamilton, May 28 2014 STATUS approved

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Last modified August 9 12:05 EDT 2022. Contains 356026 sequences. (Running on oeis4.)