|
|
A003055
|
|
Number of connected graphs, up to homeomorphism, that can be drawn in the plane using unit-length edges.
(Formerly M2464)
|
|
1
|
|
|
|
OFFSET
|
1,3
|
|
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.
|
|
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).
|
|
LINKS
|
|
|
CROSSREFS
|
|
|
KEYWORD
|
nonn,more,nice
|
|
AUTHOR
|
|
|
EXTENSIONS
|
a(9) corrected from version 5 [Jan 05 2015] of Salvia's paper; a(10) from Vaisse's webpage added by Raffaele Salvia, Jan 31 2015
|
|
STATUS
|
approved
|
|
|
|