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Search: id:A066951
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| A066951 |
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Number of nonisomorphic connected graphs that can be drawn in the plane using n unit-length edges. |
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+0
3
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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. These graphs are a subset of those counted in A046091.
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REFERENCES
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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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EXAMPLE
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Up to five edges, every planar graph can be drawn with edges of length 1, so up to this point the sequence agrees with A046091 (connected planar graphs with n edges) [except for the fact that that sequence begins with no edges]. For six edges, the only graphs that cannot be drawn with edges of length 1 are K_4 and K_{3,2}. According to A046091 there are 30 connected planar graphs with 6 edges so the sixth term is 28.
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CROSSREFS
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Cf. A003055, A002905, A046091.
Sequence in context: A161762 A005913 A056690 this_sequence A046091 A002905 A087610
Adjacent sequences: A066948 A066949 A066950 this_sequence A066952 A066953 A066954
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KEYWORD
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nonn,more,nice
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AUTHOR
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Les Reid (les(AT)math.smsu.edu), May 25, 2002
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EXTENSIONS
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a(7) = 70. - Jonathan Vos Post (jvospost3(AT)gmail.com), Jan 05 2007
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