Y = {x | x is a positive factor of the number 2^{p – 1} (2^{p} – 1), where 2^{p} – 1 is a prime number}.

Y- {x | x is a positive factor of the number 2^{p-1} (2^{p} – 1), where 2^{p} – 1 is a prime number}.

So, the factors of 2p-1 are 1,2,2^{2 },2^{3} ,…, 2^{p-1} .

Y= {1,2,2^{2} ,2^{3} , …,2^{p-1} ,2^{p} -1}