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%I A066951
%S A066951 1,1,3,5,12,28,70
%N A066951 Number of nonisomorphic connected graphs that can be drawn in the plane 
               using n unit-length edges.
%C A066951 K_4 can't be so drawn even though it is planar. These graphs are a subset 
               of those counted in A046091.
%D A066951 M. Gardner, The Unexpected Hanging and Other Mathematical Diversions. 
               Simon and Schuster, NY, 1969, p. 80.
%H A066951 Eric Weisstein's World of Mathematics, <a href="http://mathworld.wolfram.com/
               MatchProblem.html">Link to a section of The World of Mathematics.</
               a>
%e A066951 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.
%Y A066951 Cf. A003055, A002905, A046091.
%Y A066951 Sequence in context: A161762 A005913 A056690 this_sequence A046091 A002905 
               A087610
%Y A066951 Adjacent sequences: A066948 A066949 A066950 this_sequence A066952 A066953 
               A066954
%K A066951 nonn,more,nice
%O A066951 1,3
%A A066951 Les Reid (les(AT)math.smsu.edu), May 25, 2002
%E A066951 a(7) = 70. - Jonathan Vos Post (jvospost3(AT)gmail.com), Jan 05 2007

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