Sum of a (finite) hyperharmonic series











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For some $k < infty$, and $p in (0,1)$, consider the following sum:
$S_k = sum_{n=1}^{k} frac{1}{n^p}$.



What is a closed form expression for $S_k$?










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  • It may worth have a look at Hurwitz's zeta function.
    – Kemono Chen
    yesterday










  • @KemonoChen: Hurwitz's zeta function is also infinite, check generalized harmonic numbers.
    – Tianlalu
    yesterday










  • @Tianlalu You can make a subtraction from Riemann's zeta function.
    – Kemono Chen
    yesterday












  • Thanks guys. I found the answer below helpful: math.stackexchange.com/questions/451558/…
    – math_phile
    yesterday















up vote
0
down vote

favorite












For some $k < infty$, and $p in (0,1)$, consider the following sum:
$S_k = sum_{n=1}^{k} frac{1}{n^p}$.



What is a closed form expression for $S_k$?










share|cite|improve this question






















  • It may worth have a look at Hurwitz's zeta function.
    – Kemono Chen
    yesterday










  • @KemonoChen: Hurwitz's zeta function is also infinite, check generalized harmonic numbers.
    – Tianlalu
    yesterday










  • @Tianlalu You can make a subtraction from Riemann's zeta function.
    – Kemono Chen
    yesterday












  • Thanks guys. I found the answer below helpful: math.stackexchange.com/questions/451558/…
    – math_phile
    yesterday













up vote
0
down vote

favorite









up vote
0
down vote

favorite











For some $k < infty$, and $p in (0,1)$, consider the following sum:
$S_k = sum_{n=1}^{k} frac{1}{n^p}$.



What is a closed form expression for $S_k$?










share|cite|improve this question













For some $k < infty$, and $p in (0,1)$, consider the following sum:
$S_k = sum_{n=1}^{k} frac{1}{n^p}$.



What is a closed form expression for $S_k$?







integration sequences-and-series power-series






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share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked yesterday









math_phile

123




123












  • It may worth have a look at Hurwitz's zeta function.
    – Kemono Chen
    yesterday










  • @KemonoChen: Hurwitz's zeta function is also infinite, check generalized harmonic numbers.
    – Tianlalu
    yesterday










  • @Tianlalu You can make a subtraction from Riemann's zeta function.
    – Kemono Chen
    yesterday












  • Thanks guys. I found the answer below helpful: math.stackexchange.com/questions/451558/…
    – math_phile
    yesterday


















  • It may worth have a look at Hurwitz's zeta function.
    – Kemono Chen
    yesterday










  • @KemonoChen: Hurwitz's zeta function is also infinite, check generalized harmonic numbers.
    – Tianlalu
    yesterday










  • @Tianlalu You can make a subtraction from Riemann's zeta function.
    – Kemono Chen
    yesterday












  • Thanks guys. I found the answer below helpful: math.stackexchange.com/questions/451558/…
    – math_phile
    yesterday
















It may worth have a look at Hurwitz's zeta function.
– Kemono Chen
yesterday




It may worth have a look at Hurwitz's zeta function.
– Kemono Chen
yesterday












@KemonoChen: Hurwitz's zeta function is also infinite, check generalized harmonic numbers.
– Tianlalu
yesterday




@KemonoChen: Hurwitz's zeta function is also infinite, check generalized harmonic numbers.
– Tianlalu
yesterday












@Tianlalu You can make a subtraction from Riemann's zeta function.
– Kemono Chen
yesterday






@Tianlalu You can make a subtraction from Riemann's zeta function.
– Kemono Chen
yesterday














Thanks guys. I found the answer below helpful: math.stackexchange.com/questions/451558/…
– math_phile
yesterday




Thanks guys. I found the answer below helpful: math.stackexchange.com/questions/451558/…
– math_phile
yesterday










1 Answer
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I am not aware of any closed form, but there are some good approximations. The easiest way would be to approximate this sum with an integral:
$$sum_{n=1}^kn^{-p}approx1+int_1^k x^{-p}dx=1+left.frac1{1-p}x^{1-p}rightrvert^k_0=1+frac{k^{1-p}}{1-p}.$$






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    up vote
    0
    down vote



    accepted










    I am not aware of any closed form, but there are some good approximations. The easiest way would be to approximate this sum with an integral:
    $$sum_{n=1}^kn^{-p}approx1+int_1^k x^{-p}dx=1+left.frac1{1-p}x^{1-p}rightrvert^k_0=1+frac{k^{1-p}}{1-p}.$$






    share|cite|improve this answer

























      up vote
      0
      down vote



      accepted










      I am not aware of any closed form, but there are some good approximations. The easiest way would be to approximate this sum with an integral:
      $$sum_{n=1}^kn^{-p}approx1+int_1^k x^{-p}dx=1+left.frac1{1-p}x^{1-p}rightrvert^k_0=1+frac{k^{1-p}}{1-p}.$$






      share|cite|improve this answer























        up vote
        0
        down vote



        accepted







        up vote
        0
        down vote



        accepted






        I am not aware of any closed form, but there are some good approximations. The easiest way would be to approximate this sum with an integral:
        $$sum_{n=1}^kn^{-p}approx1+int_1^k x^{-p}dx=1+left.frac1{1-p}x^{1-p}rightrvert^k_0=1+frac{k^{1-p}}{1-p}.$$






        share|cite|improve this answer












        I am not aware of any closed form, but there are some good approximations. The easiest way would be to approximate this sum with an integral:
        $$sum_{n=1}^kn^{-p}approx1+int_1^k x^{-p}dx=1+left.frac1{1-p}x^{1-p}rightrvert^k_0=1+frac{k^{1-p}}{1-p}.$$







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered yesterday









        YiFan

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