%I A059103
%S A059103 1,1,2,5,13,50
%N A059103 Number of connected graphs on n points realizable in the plane with straight 
               edges all of identical length; lines are permitted to cross.
%C A059103 This counting problem is related to the well known problem to find the 
               "chromatic number of the plane"
%e A059103 a(4)=5 because the complete graph on 4 points cannot be realized in the 
               plane with all edges of equal length. All the other connected graphs 
               with 4 points can be realized.
%Y A059103 Sequence in context: A067021 A098716 A082938 this_sequence A112836 A105905 
               A075738
%Y A059103 Adjacent sequences: A059100 A059101 A059102 this_sequence A059104 A059105 
               A059106
%K A059103 hard,nonn
%O A059103 1,3
%A A059103 David Newman (dznewman(AT)netvision.net.il), Feb 13 2001