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Search: id:A003055
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| A003055 |
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Number of connected graphs, up to homeomorphism, that can be drawn in the plane using unit-length edges.
(Formerly M2464)
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+0
2
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OFFSET
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1,3
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COMMENT
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K_4 can't be so drawn even though it is planar. Although a square with a tail of length 1 and a triangle with a tail of length 2 are nonisomorphic graphs with five edges, they are homeomorphic as topological spaces.
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REFERENCES
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N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
M. Gardner, The Unexpected Hanging and Other Mathematical Diversions. Simon and Schuster, NY, 1969, p. 80.
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LINKS
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Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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CROSSREFS
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Cf. A066951.
Sequence in context: A133999 A014610 A117591 this_sequence A018101 A158568 A068013
Adjacent sequences: A003052 A003053 A003054 this_sequence A003056 A003057 A003058
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KEYWORD
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nonn,more,nice
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AUTHOR
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N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
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Corrected by Brendan McKay (bdm(AT)cs.anu.edu.au) and Les Reid (les(AT)math.smsu.edu), May 25, 2002
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