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I have tried to evaluate [tex]\Sigma[/tex] e^{-an2}so many times, but I didn't get it.

where a is just a constant and summation begin from n=1 to infinity.

I know that [tex]\Sigma[/tex]e^{n}is just geometric series which is equal 1/(1-e)

But when n changes to be n^{2}, I have no ideas how to do that.

If anyone know, please give me a suggestion.

with much thanks and appreciate!!

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# How to evaluate this summation

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