Assumptions:
- Vcc is the total voltage, whether its 5V or 3.3V.
- Imax is the maximum current you can draw.
- N is the total number of stages you want.
- The input impedance of the analog channel is high enough that makes the current flowing through the analog input insignificant.
Rtotal = Vcc/Imax
R = Rtotal/(N - 1)
Round R up to the next one or more standard resistor value for good margin.