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AL_108443783-Newcomer
3-Newcomer
December 16, 2023
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Odd summation without specific value

  • December 16, 2023
  • 1 reply
  • 1897 views

Hi 
I want to plot this summation. I would like to do it as an 'odd summation', were I don't want it to process n=2. Is there an easy solution for this problem?

AL_10844378_0-1702737598730.png

 



    Best answer by Werner_E

    I would have interpreted "odd" so that the sums should run only over the odd numbers 1,3,5,... so n=2 would be no problem at all.

     

    What do you mean by "plotting the sum"?

     

    If your sum should run from 1 up to infinity (including the even numbers) I see two ways to avoid the case n=2:

    1) use something like    if(n=2, 0, <the expression you'd like to sum up>)    in the sum

    2) Let the sum run from 3 up to infinity and add the result you get for n=1

     

    Nonetheless I would expect that n should only take od numbers as otherwise (-1)^((n+1)/2) = imaginary unit .

     

    So maybe you are looking for something like this:

    Werner_E_1-1702739022904.png

     

     

     

     

    1 reply

    W
    Werner_E25-Diamond IAnswer
    25-Diamond I
    December 16, 2023

    I would have interpreted "odd" so that the sums should run only over the odd numbers 1,3,5,... so n=2 would be no problem at all.

     

    What do you mean by "plotting the sum"?

     

    If your sum should run from 1 up to infinity (including the even numbers) I see two ways to avoid the case n=2:

    1) use something like    if(n=2, 0, <the expression you'd like to sum up>)    in the sum

    2) Let the sum run from 3 up to infinity and add the result you get for n=1

     

    Nonetheless I would expect that n should only take od numbers as otherwise (-1)^((n+1)/2) = imaginary unit .

     

    So maybe you are looking for something like this:

    Werner_E_1-1702739022904.png

     

     

     

     

    A
    AL_108443783-NewcomerAuthor
    3-Newcomer
    December 16, 2023

    Hi Werner
    Is there a way where I can make a summation of ONLY the odd numbers n=1,3,5,7..? That would solve my problem
    I tried your second option (as I could not find a way to do the first option), but it would be nice if there was a more pretty way to do it? 🙂

    AL_10844378_0-1702739321594.png

     

     

    W
    Werner_E25-Diamond I
    25-Diamond I
    December 16, 2023
    @AL_10844378 wrote:

    Hi Werner
    Is there a way where I can make a summation of ONLY the odd numbers n=1,3,5,7..? That would solve my problem

    Look at my example at the end of my previous answer.

     

    k runs from 1 to inf and instead of n I use (2*k-1) which the are the odd numbers 1,3,5,...

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