For any positive integer $n>3$, there exists at least $1$ integer $k$ such that $n+k$ and $n-k$ are...












3












$begingroup$


How to prove the following conjecture:




For any positive integer $n>3$, there exists at least $1$ integer $k$ such that $n+k$ and $n-k$ are both primes.




Any hint, idea or reference would be greatly appreciated!










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$endgroup$












  • $begingroup$
    Do you mean that $n+k$ AND $n-k$ are prime or just $n+k$ OR $n-k$ is prime?
    $endgroup$
    – stressed out
    Jan 2 at 0:28










  • $begingroup$
    both are primes
    $endgroup$
    – François Huppé
    Jan 2 at 0:32






  • 2




    $begingroup$
    But then it's false for $n<3$. Isn't it?
    $endgroup$
    – stressed out
    Jan 2 at 0:32










  • $begingroup$
    @stressed you are right
    $endgroup$
    – François Huppé
    Jan 2 at 0:35


















3












$begingroup$


How to prove the following conjecture:




For any positive integer $n>3$, there exists at least $1$ integer $k$ such that $n+k$ and $n-k$ are both primes.




Any hint, idea or reference would be greatly appreciated!










share|cite|improve this question











$endgroup$












  • $begingroup$
    Do you mean that $n+k$ AND $n-k$ are prime or just $n+k$ OR $n-k$ is prime?
    $endgroup$
    – stressed out
    Jan 2 at 0:28










  • $begingroup$
    both are primes
    $endgroup$
    – François Huppé
    Jan 2 at 0:32






  • 2




    $begingroup$
    But then it's false for $n<3$. Isn't it?
    $endgroup$
    – stressed out
    Jan 2 at 0:32










  • $begingroup$
    @stressed you are right
    $endgroup$
    – François Huppé
    Jan 2 at 0:35
















3












3








3





$begingroup$


How to prove the following conjecture:




For any positive integer $n>3$, there exists at least $1$ integer $k$ such that $n+k$ and $n-k$ are both primes.




Any hint, idea or reference would be greatly appreciated!










share|cite|improve this question











$endgroup$




How to prove the following conjecture:




For any positive integer $n>3$, there exists at least $1$ integer $k$ such that $n+k$ and $n-k$ are both primes.




Any hint, idea or reference would be greatly appreciated!







number-theory prime-numbers prime-gaps






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Jan 2 at 2:58







François Huppé

















asked Jan 2 at 0:25









François HuppéFrançois Huppé

365111




365111












  • $begingroup$
    Do you mean that $n+k$ AND $n-k$ are prime or just $n+k$ OR $n-k$ is prime?
    $endgroup$
    – stressed out
    Jan 2 at 0:28










  • $begingroup$
    both are primes
    $endgroup$
    – François Huppé
    Jan 2 at 0:32






  • 2




    $begingroup$
    But then it's false for $n<3$. Isn't it?
    $endgroup$
    – stressed out
    Jan 2 at 0:32










  • $begingroup$
    @stressed you are right
    $endgroup$
    – François Huppé
    Jan 2 at 0:35




















  • $begingroup$
    Do you mean that $n+k$ AND $n-k$ are prime or just $n+k$ OR $n-k$ is prime?
    $endgroup$
    – stressed out
    Jan 2 at 0:28










  • $begingroup$
    both are primes
    $endgroup$
    – François Huppé
    Jan 2 at 0:32






  • 2




    $begingroup$
    But then it's false for $n<3$. Isn't it?
    $endgroup$
    – stressed out
    Jan 2 at 0:32










  • $begingroup$
    @stressed you are right
    $endgroup$
    – François Huppé
    Jan 2 at 0:35


















$begingroup$
Do you mean that $n+k$ AND $n-k$ are prime or just $n+k$ OR $n-k$ is prime?
$endgroup$
– stressed out
Jan 2 at 0:28




$begingroup$
Do you mean that $n+k$ AND $n-k$ are prime or just $n+k$ OR $n-k$ is prime?
$endgroup$
– stressed out
Jan 2 at 0:28












$begingroup$
both are primes
$endgroup$
– François Huppé
Jan 2 at 0:32




$begingroup$
both are primes
$endgroup$
– François Huppé
Jan 2 at 0:32




2




2




$begingroup$
But then it's false for $n<3$. Isn't it?
$endgroup$
– stressed out
Jan 2 at 0:32




$begingroup$
But then it's false for $n<3$. Isn't it?
$endgroup$
– stressed out
Jan 2 at 0:32












$begingroup$
@stressed you are right
$endgroup$
– François Huppé
Jan 2 at 0:35






$begingroup$
@stressed you are right
$endgroup$
– François Huppé
Jan 2 at 0:35












2 Answers
2






active

oldest

votes


















6












$begingroup$

I suspect the OP means $n + k$ AND $n - k$. If so, this is the same as the strong Goldbach conjecture, which is a very well-known unsolved problem. In particular, if $n + k$ and $n - k$ are both prime, their sum is $2n$. Also, every positive even integer $gt 2$ is of the form $2n$, for some positive integer $n$. Thus, if the OP's conjecture holds, so does the Goldbach conjecture.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    @FrançoisHuppé I am not quite sure what you are stating. I never wrote that, or meant to imply, it was "trivial". I just explained that it is a slightly stronger conjecture than the strong Goldbach conjecture. I was not aware from your question that you already knew this, and I didn't mean to imply you did not because there is no way for me to know what you have already figured out apart from what you wrote.
    $endgroup$
    – John Omielan
    Jan 2 at 0:49












  • $begingroup$
    sorry it came out wrong, i should add this in my question instead :) in fact your answer is perfect
    $endgroup$
    – François Huppé
    Jan 2 at 0:58










  • $begingroup$
    @FrançoisHuppé No worries about your earlier comment. Also, I originally thought your question said $k$ is a positive integer. Perhaps it did then but was changed since as I see the question has an edit time after my answer. Regardless, as the question text now does not require this, it means your conjecture is the same as the Goldbach one, so I have changed my answer accordingly to no longer say yours is a slightly stronger conjecture.
    $endgroup$
    – John Omielan
    Jan 2 at 7:58



















2












$begingroup$

I would do some searching in the On-Line Encyclopedia of Integer Sequences (OEIS). Give me a couple of minutes...



Okay, here's one pertinent result: http://oeis.org/A020483 Least prime $p$ such that $p + 2n$ is also prime. According to Jens Kruse Andersen, "It is conjectured that $a(n)$ always exists."






share|cite|improve this answer









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    2 Answers
    2






    active

    oldest

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    6












    $begingroup$

    I suspect the OP means $n + k$ AND $n - k$. If so, this is the same as the strong Goldbach conjecture, which is a very well-known unsolved problem. In particular, if $n + k$ and $n - k$ are both prime, their sum is $2n$. Also, every positive even integer $gt 2$ is of the form $2n$, for some positive integer $n$. Thus, if the OP's conjecture holds, so does the Goldbach conjecture.






    share|cite|improve this answer











    $endgroup$













    • $begingroup$
      @FrançoisHuppé I am not quite sure what you are stating. I never wrote that, or meant to imply, it was "trivial". I just explained that it is a slightly stronger conjecture than the strong Goldbach conjecture. I was not aware from your question that you already knew this, and I didn't mean to imply you did not because there is no way for me to know what you have already figured out apart from what you wrote.
      $endgroup$
      – John Omielan
      Jan 2 at 0:49












    • $begingroup$
      sorry it came out wrong, i should add this in my question instead :) in fact your answer is perfect
      $endgroup$
      – François Huppé
      Jan 2 at 0:58










    • $begingroup$
      @FrançoisHuppé No worries about your earlier comment. Also, I originally thought your question said $k$ is a positive integer. Perhaps it did then but was changed since as I see the question has an edit time after my answer. Regardless, as the question text now does not require this, it means your conjecture is the same as the Goldbach one, so I have changed my answer accordingly to no longer say yours is a slightly stronger conjecture.
      $endgroup$
      – John Omielan
      Jan 2 at 7:58
















    6












    $begingroup$

    I suspect the OP means $n + k$ AND $n - k$. If so, this is the same as the strong Goldbach conjecture, which is a very well-known unsolved problem. In particular, if $n + k$ and $n - k$ are both prime, their sum is $2n$. Also, every positive even integer $gt 2$ is of the form $2n$, for some positive integer $n$. Thus, if the OP's conjecture holds, so does the Goldbach conjecture.






    share|cite|improve this answer











    $endgroup$













    • $begingroup$
      @FrançoisHuppé I am not quite sure what you are stating. I never wrote that, or meant to imply, it was "trivial". I just explained that it is a slightly stronger conjecture than the strong Goldbach conjecture. I was not aware from your question that you already knew this, and I didn't mean to imply you did not because there is no way for me to know what you have already figured out apart from what you wrote.
      $endgroup$
      – John Omielan
      Jan 2 at 0:49












    • $begingroup$
      sorry it came out wrong, i should add this in my question instead :) in fact your answer is perfect
      $endgroup$
      – François Huppé
      Jan 2 at 0:58










    • $begingroup$
      @FrançoisHuppé No worries about your earlier comment. Also, I originally thought your question said $k$ is a positive integer. Perhaps it did then but was changed since as I see the question has an edit time after my answer. Regardless, as the question text now does not require this, it means your conjecture is the same as the Goldbach one, so I have changed my answer accordingly to no longer say yours is a slightly stronger conjecture.
      $endgroup$
      – John Omielan
      Jan 2 at 7:58














    6












    6








    6





    $begingroup$

    I suspect the OP means $n + k$ AND $n - k$. If so, this is the same as the strong Goldbach conjecture, which is a very well-known unsolved problem. In particular, if $n + k$ and $n - k$ are both prime, their sum is $2n$. Also, every positive even integer $gt 2$ is of the form $2n$, for some positive integer $n$. Thus, if the OP's conjecture holds, so does the Goldbach conjecture.






    share|cite|improve this answer











    $endgroup$



    I suspect the OP means $n + k$ AND $n - k$. If so, this is the same as the strong Goldbach conjecture, which is a very well-known unsolved problem. In particular, if $n + k$ and $n - k$ are both prime, their sum is $2n$. Also, every positive even integer $gt 2$ is of the form $2n$, for some positive integer $n$. Thus, if the OP's conjecture holds, so does the Goldbach conjecture.







    share|cite|improve this answer














    share|cite|improve this answer



    share|cite|improve this answer








    edited Jan 2 at 7:52

























    answered Jan 2 at 0:35









    John OmielanJohn Omielan

    3,5651215




    3,5651215












    • $begingroup$
      @FrançoisHuppé I am not quite sure what you are stating. I never wrote that, or meant to imply, it was "trivial". I just explained that it is a slightly stronger conjecture than the strong Goldbach conjecture. I was not aware from your question that you already knew this, and I didn't mean to imply you did not because there is no way for me to know what you have already figured out apart from what you wrote.
      $endgroup$
      – John Omielan
      Jan 2 at 0:49












    • $begingroup$
      sorry it came out wrong, i should add this in my question instead :) in fact your answer is perfect
      $endgroup$
      – François Huppé
      Jan 2 at 0:58










    • $begingroup$
      @FrançoisHuppé No worries about your earlier comment. Also, I originally thought your question said $k$ is a positive integer. Perhaps it did then but was changed since as I see the question has an edit time after my answer. Regardless, as the question text now does not require this, it means your conjecture is the same as the Goldbach one, so I have changed my answer accordingly to no longer say yours is a slightly stronger conjecture.
      $endgroup$
      – John Omielan
      Jan 2 at 7:58


















    • $begingroup$
      @FrançoisHuppé I am not quite sure what you are stating. I never wrote that, or meant to imply, it was "trivial". I just explained that it is a slightly stronger conjecture than the strong Goldbach conjecture. I was not aware from your question that you already knew this, and I didn't mean to imply you did not because there is no way for me to know what you have already figured out apart from what you wrote.
      $endgroup$
      – John Omielan
      Jan 2 at 0:49












    • $begingroup$
      sorry it came out wrong, i should add this in my question instead :) in fact your answer is perfect
      $endgroup$
      – François Huppé
      Jan 2 at 0:58










    • $begingroup$
      @FrançoisHuppé No worries about your earlier comment. Also, I originally thought your question said $k$ is a positive integer. Perhaps it did then but was changed since as I see the question has an edit time after my answer. Regardless, as the question text now does not require this, it means your conjecture is the same as the Goldbach one, so I have changed my answer accordingly to no longer say yours is a slightly stronger conjecture.
      $endgroup$
      – John Omielan
      Jan 2 at 7:58
















    $begingroup$
    @FrançoisHuppé I am not quite sure what you are stating. I never wrote that, or meant to imply, it was "trivial". I just explained that it is a slightly stronger conjecture than the strong Goldbach conjecture. I was not aware from your question that you already knew this, and I didn't mean to imply you did not because there is no way for me to know what you have already figured out apart from what you wrote.
    $endgroup$
    – John Omielan
    Jan 2 at 0:49






    $begingroup$
    @FrançoisHuppé I am not quite sure what you are stating. I never wrote that, or meant to imply, it was "trivial". I just explained that it is a slightly stronger conjecture than the strong Goldbach conjecture. I was not aware from your question that you already knew this, and I didn't mean to imply you did not because there is no way for me to know what you have already figured out apart from what you wrote.
    $endgroup$
    – John Omielan
    Jan 2 at 0:49














    $begingroup$
    sorry it came out wrong, i should add this in my question instead :) in fact your answer is perfect
    $endgroup$
    – François Huppé
    Jan 2 at 0:58




    $begingroup$
    sorry it came out wrong, i should add this in my question instead :) in fact your answer is perfect
    $endgroup$
    – François Huppé
    Jan 2 at 0:58












    $begingroup$
    @FrançoisHuppé No worries about your earlier comment. Also, I originally thought your question said $k$ is a positive integer. Perhaps it did then but was changed since as I see the question has an edit time after my answer. Regardless, as the question text now does not require this, it means your conjecture is the same as the Goldbach one, so I have changed my answer accordingly to no longer say yours is a slightly stronger conjecture.
    $endgroup$
    – John Omielan
    Jan 2 at 7:58




    $begingroup$
    @FrançoisHuppé No worries about your earlier comment. Also, I originally thought your question said $k$ is a positive integer. Perhaps it did then but was changed since as I see the question has an edit time after my answer. Regardless, as the question text now does not require this, it means your conjecture is the same as the Goldbach one, so I have changed my answer accordingly to no longer say yours is a slightly stronger conjecture.
    $endgroup$
    – John Omielan
    Jan 2 at 7:58











    2












    $begingroup$

    I would do some searching in the On-Line Encyclopedia of Integer Sequences (OEIS). Give me a couple of minutes...



    Okay, here's one pertinent result: http://oeis.org/A020483 Least prime $p$ such that $p + 2n$ is also prime. According to Jens Kruse Andersen, "It is conjectured that $a(n)$ always exists."






    share|cite|improve this answer









    $endgroup$


















      2












      $begingroup$

      I would do some searching in the On-Line Encyclopedia of Integer Sequences (OEIS). Give me a couple of minutes...



      Okay, here's one pertinent result: http://oeis.org/A020483 Least prime $p$ such that $p + 2n$ is also prime. According to Jens Kruse Andersen, "It is conjectured that $a(n)$ always exists."






      share|cite|improve this answer









      $endgroup$
















        2












        2








        2





        $begingroup$

        I would do some searching in the On-Line Encyclopedia of Integer Sequences (OEIS). Give me a couple of minutes...



        Okay, here's one pertinent result: http://oeis.org/A020483 Least prime $p$ such that $p + 2n$ is also prime. According to Jens Kruse Andersen, "It is conjectured that $a(n)$ always exists."






        share|cite|improve this answer









        $endgroup$



        I would do some searching in the On-Line Encyclopedia of Integer Sequences (OEIS). Give me a couple of minutes...



        Okay, here's one pertinent result: http://oeis.org/A020483 Least prime $p$ such that $p + 2n$ is also prime. According to Jens Kruse Andersen, "It is conjectured that $a(n)$ always exists."







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Jan 2 at 5:08









        Robert SoupeRobert Soupe

        11.3k21950




        11.3k21950






























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