hello guys, 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]en is just geometric series which is equal 1/(1-e) But when n changes to be n2, I have no ideas how to do that. If anyone know, please give me a suggestion. with much thanks and appreciate!!