Y = {x | x is a positive factor of the number 2p – 1 (2p – 1), where 2p – 1 is a prime number}.
Y- {x | x is a positive factor of the number 2p-1 (2p – 1), where 2p – 1 is a prime number}.
So, the factors of 2p-1 are 1,2,22 ,23 ,…, 2p-1 .
Y= {1,2,22 ,23 , …,2p-1 ,2p -1}