I need to determine the interval of convergence of the power series
sum of series
I have got as far as
Here An=1/(3n5^n), for n=1,2,...
|An+1/An|=1/(3n+1)5^n+1 times 3n5^n/1
= 1/(3n+1/n)^5 ---> 1/5 as n ----> infinity.
We have R=5, by the Ratio Test. Since a=?
Can anyone help?