Any system of 
integers, where 
is the totient function, representing all the
residue classes relatively
prime to 
is called a reduced residue system (Nagell 1951, p. 71).
Reduced Residue System
See also
Complete Residue System, Residue ClassExplore with Wolfram|Alpha
References
Nagell, T. "Residue Classes and Residue Systems." §20 in Introduction to Number Theory. New York: Wiley, pp. 69-71, 1951.Referenced on Wolfram|Alpha
Reduced Residue SystemCite this as:
Weisstein, Eric W. "Reduced Residue System." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/ReducedResidueSystem.html