A system in which a strange loop appears.
Tangled Hierarchy
See also
Strange LoopExplore with Wolfram|Alpha
References
Hofstadter, D. R. Gödel, Escher, Bach: An Eternal Golden Braid. New York: Vintage Books, p. 10, 1989.Referenced on Wolfram|Alpha
Tangled HierarchyCite this as:
Weisstein, Eric W. "Tangled Hierarchy." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/TangledHierarchy.html