I have doubts of how to make the connection between a unipolar stepper motor of 5 wires an the 4 pins of a pololu a4998 driver. I do not know how to identify the coils of the stepper.
If you know any scheme or a webpage where this is explained please tell me.
I wish all questions were so simple.
An A4988 is for driving bipolar stepper motors.
If you have one of the small 28byj steppers they are usually driven using a ULN2003.
In some 5-wire steppers you can separate the 5th wire into two so that the the two coils are electrically separate. Then you can ignore the wires to the centres of the coils and treat the motor as a 4-wire bipolar motor. But the two coils must be electrically separate.
Stepper Motor Basics
Yes, the rule is 4, 6 and 8 wire can be driven from a chopper or dual H-bridge,
5, 6 and 8 can be driven unipolar.
8 wire motors can be driven with windings in series or parallel if treated as bipolar.