Mersenne conjectures

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In mathematics, the Mersenne conjectures concern the characterization of prime numbers of a form called Mersenne primes.

The original, called Mersenne's conjecture, was a statement by Marin Mersenne in his Cogitata Physica-Mathematica (1644; see e.g. Dickson 1919) that the numbers 2ⁿ − 1 were prime for n = 2, 3, 5, 7, 13, 17, 19, 31, 67, 127 and 257, and were composite for all other positive integers n < 257. Due to the size of these numbers, Mersenne did not and could not test all of them, nor could his peers in the 17th century. It was eventually determined, after three centuries and the availability of new techniques such as the Lucas–Lehmer test, that Mersenne's conjecture contained five errors, namely two listed composites (n = 67, 257) and three omitted primes (n = 61, 89, 107). The correct list is: n = 2, 3, 5, 7, 13, 17, 19, 31, 61, 89, 107 and 127.

While Mersenne's original conjecture is false, it has led to the New Mersenne conjecture and the Lenstra–Pomerance–Wagstaff conjecture.

Contents 1 New Mersenne conjecture 2 Lenstra–Pomerance–Wagstaff conjecture 3 See also 4 References 5 External links

[edit] New Mersenne conjecture

The New Mersenne conjecture or Bateman, Selfridge and Wagstaff conjecture (Bateman et al. 1989) states that for any odd natural number p, if any two of the following conditions hold, then so does the third:

1. p = 2^k ± 1 or p = 4^k ± 3 for some natural number k.
2. 2^p − 1 is prime (a Mersenne prime).
3. (2^p + 1) / 3 is prime (a Wagstaff prime).

If p is an odd composite number, then 2^p − 1 and (2^p + 1)/3 are both composite. Therefore it is only necessary to test odd primes to verify the truth of the conjecture.

The New Mersenne conjecture can be thought of as an attempt to salvage the centuries-old Mersenne's conjecture, which is false.

Renaud Lifchitz has shown that the NMC is true up to 12,441,900 by systematically testing all odd primes for which it is already known that one of the conditions holds. His website documents the verification of results up to this number.

[edit] Lenstra–Pomerance–Wagstaff conjecture

Lenstra, Pomerance, and Wagstaff have conjectured that not only are there an infinite number of Mersenne primes, meaning prime numbers of the form

2^p − 1,

but that the number of Mersenne primes with exponent p less than x is asymptotically approximated by

,

where γ is the Euler-Mascheroni constant, and

[edit] See also

• Lucas–Lehmer test (general)
• Lucas–Lehmer test for Mersenne numbers

[edit] References

• Bateman, P. T.; Selfridge, J. L.; Wagstaff, Jr., Samuel S. (1989). "The new Mersenne conjecture". American Mathematical Monthly 96: 125–128. MR0992073. 

• Dickson, L. E. (1919). History of the Theory of Numbers. Carnegie Institute of Washington.  Reprinted by Chelsea Publishing, New York, 1971.

[edit] External links

• The Prime Pages. Mersenne's conjecture.