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enter image description here I have tried this

Sum[4 *j* ChebyshevT[m, 2 x/l - 1] /l  EvenQ[j + m - 1]  , {m, 1,j - 1}, {j, 1, 10}] 

But I got 0


put on hold as off-topic by J. M. will be back soon 2 days ago

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  • "This question cannot be answered without additional information. Questions on problems in code must describe the specific problem and include valid code to reproduce it. Any data used for programming examples should be embedded in the question or code to generate the (fake) data must be included." – J. M. will be back soon
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  • $\begingroup$ Quick note: you want to use Boole[EvenQ[...]] instead of just EvenQ[...]. Also, where is $\xi_m$ in your code? $\endgroup$ – AccidentalFourierTransform Aug 16 at 13:17
  • $\begingroup$ This is a little unclear. Can you at least provide a reference for where this expression came from? $\endgroup$ – J. M. will be back soon 2 days ago

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