I cannot figure out how to write this series in formula summation form. I know it is an alternating series. So far I have:

a_n(n=0 to infiniti) = (-1)^n(3^2n)/(something)

I cannot determine the denominator...

I believe there was also a mistake on the printout of the problem. The third term of the series is supposed to be (2^2)(4^2).

Thank you for any help!