One of the seven 4-polyhexes. S. Kim has observed that four worms solve the puzzle of finding a non-three-colorable map with only four congruent countries (as long as no lakes are allowed).
Worm
See also
Three-Colorable Map, TurmiteExplore with Wolfram|Alpha
References
Gardner, M. Mathematical Magic Show: More Puzzles, Games, Diversions, Illusions and Other Mathematical Sleight-of-Mind from Scientific American. New York: Vintage, p. 147, 1978.Gosper, R. W. G. "Quattroslabia." http://www.ippi.com/rwg/Quattroslabia.htm.Referenced on Wolfram|Alpha
WormCite this as:
Weisstein, Eric W. "Worm." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Worm.html