# Double series

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Hello,

I need your help to calculate (approximate) a double series as shown in the attached.

Thank you so much.

Best,

Steve.double_series.pdf

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Without any information about f(i), it can't be done.

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Hello mathematic,

The function f(i) = |2*i - A|, A is a constant.

Best,

Steve.

double_series.pdf

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In the denominator does 2^k multiply j or j+i?

Edited by mathematic
structure
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[(2^k multiply j) + i] in the denominator.

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On 2/2/2019 at 10:13 PM, mathematic said:

$\sum_{i=1}^n\sum{j=1}^n\frac{|2i-A|}{2^kj+i}=\sum_{i=1}^n\frac{|2i-A|}{2^k}\sum{j=1}^n\frac{1}{j+2^{-k}i}\approx \sum_{i=1}^n\frac{|2i-A|}{2^k}(ln{n+2^{-k}i})-ln(2^{-k}i))$.

See if you can start here.  I am trying to use Latex - not working.

Edited by Strange
latex problem
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Hello everyone,

Is there any update for this problem?

Best regards,

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I can't get at my last post to try to fix it.  Essentially I tried to rearrange things so that the j summation could be carried out.

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Edited by mathematic
remove underline
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Thank you so much. If you have any update, let me know. I'm very appreciated to get your help.

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• 4 months later...

First I was wondering by what calculate means, but eitherway i dont think there is a closed form.

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On 2/7/2019 at 10:10 PM, mathematic said:

I can't get at my last post to try to fix it.  Essentially I tried to rearrange things so that the j summation could be carried out.

I think I fixed your Latex (no idea if it is correct or not!)

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