Thank you Dr. Maan, numbers of the form 2^n-1 are called Mersenne numbers and not necessarily prime, but when 2^n-1 is prime it is said to be a Mersenne prime.
Thank you very much, I agree with you that Lucas-Lehmer test is the best for Mersenne primes. I am intrested in your paper i find it very useful in my research feild.
There is no formula to generate the next prime number of the form 2^p - 1. If there were, there would be no need to verify that they are prime like what the "Great Internet Mersenne Prime Search" does with distributed computing:
Mersenne was looking for a formula that would generate all the prime numbers. ... These numbers are now called Mersenne numbers or Mersenne primes. In 1644 he wrote that Mp is prime for p = 2, 3, 5, 7, 13, 17, 19, 31, 67, 127, 257, and compound – in other words, non-prime – for the other 44 lower p values at 257
Also, It can be seen, that when written in binary form, Mersenne primes consist of only the digit 1. If there are n digits in any Mersenne prime written in binary form, then, the binary number, written as n 1's followed by (n-1) 0's represents a perfect number. as we see here,
Mersenne prime in decimal form, 3, 7, 31, 127, 2047, 8191, 131071, 524287 , ...
Mersenne prime in binary form, 11, 111, 11111, 1111111, 1111111111111, 11111111111111111, ...
Perfect numbers that corresponding to above Mersenne primes,
yes, it is a great unsolved problem, and if the even perfect number , with Mersenne prime, the problem How to find perfect number?? it's a good question!, this is a need to answer!
There is a one to one correspondence between Mersenne primes and the even perfect numbers. That is, if 2p - 1 is Mersenne prime, then 2p-1 ( 2p - 1) is an even perfect number.
Conversely, any even perfect number should have the form 2p-1 ( 2p - 1)
where 2p - 1 is a Mersenne prime.
One of the main interesting unsolved problems in number theory:
Is there any odd perfect number?
Here are some interesting properties about the odd perfect number if exist:
(1) It has the form 12k+1 or 36k + 9.
(2) It is not divisible by 3,5 or 7.
(3) It has at least 27 distinct prime factors.
(4) It has at least 101 prime factors.(not necessarily distinct)
(5) It also has the form (4p+1)4k+1 m2 where 4p+1 is prime.
(6) If N is perfect number, then N2-w(N) ≤ (1/3)(2/3)w(N)-1
where w(N) is the number of distinct prime factors of N.
Although, Mersenne primes and Mersenne numbers have huge literature commenting in their properties and uses, however it is equally worthwhile to mention that Mersenne numbers are also not described completely. One may think of perfect numbers associated with Mersenne numbers but that is just one application of mersenne numbers. Questions like why all mersenne numbers are squarefree are still unproven.