EGINNING A PROOF: Proving 2n-1 is Prime for all n

[brad sue]

Hi I have difficulty to begin with this problem:

prove or disapprove that 2ⁿ-1 is prime for all non negative integers n.

I know the definition of a prime number but how to apply it for this proof?

Please, can I have a suggestion to start this problem?

B

 

[StatusX]

Try some values of n and see if you can find a composite number (hint: I wouldn't be telling you to do this unless your search would end eventually).