Is there a singularity in this expression ? Need help with an explanation. How to correct this expression ?

[lvl107]

Hello Everybody.

Is there a singularity in this expression ? Need help with an explanation.

How to correct this expression ?

Thank you in advance.

Best Regards.

[RichardJ · Accepted solution]

If you symbolically evaluate the inner two sums you will see that MuPad gives an expression that contains Gamma(1-j). That means when j=1 you have Gamma(0), which is your singularity.