Unclear on step #2 of the MathWorld definition of the Reimann Prime Counting Function











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I was reading through the MathWorld article on the Reimann Prime Counting Function.



The first step in the definition is clear to me:



$$f(x) = sum_{p^v < x text{ and p prime}} frac{1}{v}$$



Here is the second step:



$$=sum_{n}frac{pi(x^{1/n})}{n}$$



It is not clear to me how the sum of the reciprocal of the power is equal to the sum of the prime counting function divided by all values of $n$.



I would appreciate if someone could show how the second step follows from the first.










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    up vote
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    down vote

    favorite
    1












    I was reading through the MathWorld article on the Reimann Prime Counting Function.



    The first step in the definition is clear to me:



    $$f(x) = sum_{p^v < x text{ and p prime}} frac{1}{v}$$



    Here is the second step:



    $$=sum_{n}frac{pi(x^{1/n})}{n}$$



    It is not clear to me how the sum of the reciprocal of the power is equal to the sum of the prime counting function divided by all values of $n$.



    I would appreciate if someone could show how the second step follows from the first.










    share|cite|improve this question
























      up vote
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      down vote

      favorite
      1









      up vote
      0
      down vote

      favorite
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      1





      I was reading through the MathWorld article on the Reimann Prime Counting Function.



      The first step in the definition is clear to me:



      $$f(x) = sum_{p^v < x text{ and p prime}} frac{1}{v}$$



      Here is the second step:



      $$=sum_{n}frac{pi(x^{1/n})}{n}$$



      It is not clear to me how the sum of the reciprocal of the power is equal to the sum of the prime counting function divided by all values of $n$.



      I would appreciate if someone could show how the second step follows from the first.










      share|cite|improve this question













      I was reading through the MathWorld article on the Reimann Prime Counting Function.



      The first step in the definition is clear to me:



      $$f(x) = sum_{p^v < x text{ and p prime}} frac{1}{v}$$



      Here is the second step:



      $$=sum_{n}frac{pi(x^{1/n})}{n}$$



      It is not clear to me how the sum of the reciprocal of the power is equal to the sum of the prime counting function divided by all values of $n$.



      I would appreciate if someone could show how the second step follows from the first.







      prime-numbers proof-explanation






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      asked Nov 19 at 17:00









      Larry Freeman

      3,24721239




      3,24721239






















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          Hint:



          How many $v$-th powers of primes are there between $1$ and $x$?



          Answer: if $p$ is a prime then $p^v<x$ iff $p<x^{1/v}$. Then the number of $v$-th powers of primes between $1$ and $x$ is $pi(x^{1/v})$.






          share|cite|improve this answer























          • the product of these numbers is the least common multiple of $x$.
            – Larry Freeman
            Nov 19 at 17:09












          • Now, I am clear. Thanks!
            – Larry Freeman
            Nov 19 at 23:54











          Your Answer





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          1 Answer
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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

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          active

          oldest

          votes








          up vote
          1
          down vote



          accepted










          Hint:



          How many $v$-th powers of primes are there between $1$ and $x$?



          Answer: if $p$ is a prime then $p^v<x$ iff $p<x^{1/v}$. Then the number of $v$-th powers of primes between $1$ and $x$ is $pi(x^{1/v})$.






          share|cite|improve this answer























          • the product of these numbers is the least common multiple of $x$.
            – Larry Freeman
            Nov 19 at 17:09












          • Now, I am clear. Thanks!
            – Larry Freeman
            Nov 19 at 23:54















          up vote
          1
          down vote



          accepted










          Hint:



          How many $v$-th powers of primes are there between $1$ and $x$?



          Answer: if $p$ is a prime then $p^v<x$ iff $p<x^{1/v}$. Then the number of $v$-th powers of primes between $1$ and $x$ is $pi(x^{1/v})$.






          share|cite|improve this answer























          • the product of these numbers is the least common multiple of $x$.
            – Larry Freeman
            Nov 19 at 17:09












          • Now, I am clear. Thanks!
            – Larry Freeman
            Nov 19 at 23:54













          up vote
          1
          down vote



          accepted







          up vote
          1
          down vote



          accepted






          Hint:



          How many $v$-th powers of primes are there between $1$ and $x$?



          Answer: if $p$ is a prime then $p^v<x$ iff $p<x^{1/v}$. Then the number of $v$-th powers of primes between $1$ and $x$ is $pi(x^{1/v})$.






          share|cite|improve this answer














          Hint:



          How many $v$-th powers of primes are there between $1$ and $x$?



          Answer: if $p$ is a prime then $p^v<x$ iff $p<x^{1/v}$. Then the number of $v$-th powers of primes between $1$ and $x$ is $pi(x^{1/v})$.







          share|cite|improve this answer














          share|cite|improve this answer



          share|cite|improve this answer








          edited Nov 19 at 17:12

























          answered Nov 19 at 17:05









          ajotatxe

          52.3k23789




          52.3k23789












          • the product of these numbers is the least common multiple of $x$.
            – Larry Freeman
            Nov 19 at 17:09












          • Now, I am clear. Thanks!
            – Larry Freeman
            Nov 19 at 23:54


















          • the product of these numbers is the least common multiple of $x$.
            – Larry Freeman
            Nov 19 at 17:09












          • Now, I am clear. Thanks!
            – Larry Freeman
            Nov 19 at 23:54
















          the product of these numbers is the least common multiple of $x$.
          – Larry Freeman
          Nov 19 at 17:09






          the product of these numbers is the least common multiple of $x$.
          – Larry Freeman
          Nov 19 at 17:09














          Now, I am clear. Thanks!
          – Larry Freeman
          Nov 19 at 23:54




          Now, I am clear. Thanks!
          – Larry Freeman
          Nov 19 at 23:54


















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