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A243013
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Number of graphs with n vertices and n-1 edges that can be gracefully labeled.
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0
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OFFSET
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1,4
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COMMENTS
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Hand calculated by grade 3 students up to term 6: (1,1,1,3,5,12...)
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LINKS
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Table of n, a(n) for n=1..7.
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EXAMPLE
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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: ∆ / .
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CROSSREFS
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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
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KEYWORD
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more,nonn
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AUTHOR
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Gordon Hamilton, May 28 2014
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STATUS
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approved
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