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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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1
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OFFSET
| 1,3
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COMMENTS
| 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
| M. Gardner, The Unexpected Hanging and Other Mathematical Diversions. Simon and Schuster, NY, 1969, p. 80.
R. C. Read, From Forests to Matches, Journal of Recreational Mathematics, Vol. 1:3 (Jul 1968), 60-172.
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
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LINKS
| Eric Weisstein's World of Mathematics, Link to a section of The World of Mathematics.
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CROSSREFS
| Cf. A066951.
Sequence in context: A133999 A014610 A117591 * A018101 A158568 A068013
Adjacent sequences: A003052 A003053 A003054 * A003056 A003057 A003058
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KEYWORD
| nonn,more,nice
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com).
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EXTENSIONS
| Corrected by Brendan McKay (bdm(AT)cs.anu.edu.au) and Les Reid (les(AT)math.smsu.edu), May 25 2002
Reference added. a(8)=84 from Read's paper. William Rex Marshall, Nov 16 2010
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