string question

[Physicsissuef]

1. The problem statement, all variables and given/known data

Determine the formula of this string:

2,4,8, ...


2. Relevant equations



3. The attempt at a solution

How will I determine the formula of this string? Is there any general formula, or I am let on my own to determine what it is?

Thank you.

[symbolipoint]

Why do you call, "2, 4, 8, ..." a string? Could you call it a sequence?

Using "2" as the first term, how is the next term determined? How is the term after that one determined? The fourth term is not shown, but the pattern continues.

[Physicsissuef]

a_n=2^n

But there is another one.