Using a 'random' function in sketch gives same pattern of numbers every-time. But, I need to generate different numbers such that any number to repeat itself should have a very less probability.
The standard (but not very good) solution is to seed the random number generator from an
analogRead() on an unconnected pin. For better options, see this answer to a related question.
Allocate 4 bytes in EEPROM to save a seed value.
Use the EEPROM library (#include ). Use EEPROM.put() and EEPROM.get() functions to write and read the seed value to EEPROM.
In setup(): Read the seed_value from EEPROM, increment it and write it back to EEPROM. Then call randomSeed(seed_value).
Now, after every run of setup(), random() will create a whole new random sequence. If you need a new sequence within your sketch, you can repeat the process, and don't forget to write the new seed to EEPROM for next time.
Note that I didn't bother with initialising the EEPROM value the first time we run. It'll probably be zero when you start a new Arduino board, but the only thing that matters is that you increment it each run. Incrementing by 1 will do the trick, but any increment value will probably do.