Let denote the set of the numbers less than and Relatively Prime to , where is the
Totient Function. Define
See also Leudesdorf Theorem
Hardy, G. H. and Wright, E. M. ``Bauer's Identical Congruence.'' §8.5 in
An Introduction to the Theory of Numbers, 5th ed. Oxford, England: Clarendon Press, pp. 98-100, 1979.