Answer:
It does not exist.
Explanation:
If we divide the second term by the first, 3rd by the 2nd and the 4th by the 3rd we get a constant result 4/3.
So this is a Geometric Series with common ratio r = 4/3 and a1 = 1/3.
As the common ratio is greater than 1 the series diverges ( continues to get bigger) so there is no sum to infinity. It just goes on getting bigger and bigger without bounds.