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Difference between revisions of "Liskovets-Gallot conjectures"

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The '''Liskovets-Gallot conjectures''' are a family of conjectures regarding the frequency of prime {{Vn}}-values of a given parity for Riesel and Proth {{Vk}}-values divisible by 3. The notion that certain {{Vk}}-values, divisible by 3, have no prime {{Vn}}-values of a given parity was first conjectured by [[Valery Liskovets]] in 2001. [[Yves Gallot]] found suitable non-trivial {{Vk}}-values for all four sign/parity combinations shortly thereafter and claimed them to be the smallest such {{Vk}}-values, thus forming the conjectures' final form. A search was started by [[Conjectures 'R Us|CRUS]] in 2008 to prove the conjectures by finding primes of the required parity for all smaller {{Vk}}-values. The even Proth conjecture was proven in 2015, and CRUS is continuing the [[CRUS Liskovets-Gallot]] subproject to find the remaining 9 primes required to prove the other 3 conjectures.
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==Definitions==
 
==Definitions==
 
[[Valery Liskovets]] studied the list of {{Kbn|+|k|n}} primes and observed, that the {{Vk}}'s ({{Vk}} divisible by 3)
 
[[Valery Liskovets]] studied the list of {{Kbn|+|k|n}} primes and observed, that the {{Vk}}'s ({{Vk}} divisible by 3)

Revision as of 13:06, 6 April 2022

The Liskovets-Gallot conjectures are a family of conjectures regarding the frequency of prime n-values of a given parity for Riesel and Proth k-values divisible by 3. The notion that certain k-values, divisible by 3, have no prime n-values of a given parity was first conjectured by Valery Liskovets in 2001. Yves Gallot found suitable non-trivial k-values for all four sign/parity combinations shortly thereafter and claimed them to be the smallest such k-values, thus forming the conjectures' final form. A search was started by CRUS in 2008 to prove the conjectures by finding primes of the required parity for all smaller k-values. The even Proth conjecture was proven in 2015, and CRUS is continuing the CRUS Liskovets-Gallot subproject to find the remaining 9 primes required to prove the other 3 conjectures.

Definitions

Valery Liskovets studied the list of k•2n+1 primes and observed, that the k's (k divisible by 3) got an irregular contribution of odd and even exponents yielding a prime.

Examples: (for 1 ≤ n ≤ 100000)

k-value # odd # even
51 38 5
231 51 9
261 56 14
87 2 36
93 1 38
177 8 46

So Liskovets formulated the conjecture:

There exist k, 3|k, such that primes k•2n+1 do exist but only with odd n/only with even n.

Yves Gallot extended this for k•2n-1 numbers and gave also the first solutions as:

k•2n+1 is composite for all even n for k=66741
k•2n+1 is composite for all odd n for k=95283
k•2n-1 is composite for all even n for k=39939
k•2n-1 is composite for all odd n for k=172677

Proof

The verification of these conjectures has to be done in the same manner like the Riesel problem: find a prime for all k-values less than the given with the needed condition.

Search

The current search is maintained by the Conjectures 'R Us project and can be found here.

Links