Perfect Difference Set
A Set of Residues 
(mod 
) such that everyNonzero Residue can be uniquely expressed in the form 
. Examples include
(mod 7) and 
(mod 13). A Necessary condition for a difference set to exist is that be of the form 
. A Sufficient condition is that 
be a Prime Power. Perfect sets can be usedin the construction of Perfect Rulers.
References
Guy, R. K. ``Modular Difference Sets and Error Correcting Codes.'' §C10 in Unsolved Problems in Number Theory, 2nd ed. New York: Springer-Verlag, pp. 118-121, 1994.
- Archimedes' Spiral Inverse
- Arc Length
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- Area Element
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