  Quantum Hall effect (QHE) is the basis of modern resistance metrology. In
Quantum Hall Array Resistance Standards (QHARS), several individual QHE
elements, each one having the same QHE resistance (typically half of the von
Klitzing constant), are arranged in networks that realize resistance values
close to decadic values (such as 1 kiloohm or 100 kiloohm), of direct interest
for dissemination. The same decadic value can be approximated with different
grades of precision, and even for the same approximation several networks of
QHE elements can be conceived. The paper investigates the design of QHARS
networks by giving methods to find a proper approximation of the resistance of
interest, and to design the corresponding network with a small number of
elements. Results for several decadic cases are given.
