Question

What is the sum of the series?

Answer 1

 4 + 12 + 36... etc
is a sum that can be rewritten in form

 4 ( 1, 3, 9, 27, 81, etc) this can further be written in sigma notation:

4 Sigma [ 3 ^ ( i - 1)]

The sum of the indefinite summation will be the limit as i goes to infinity = infinity