What does this notation mean $\{a_k\}_{k=i}^n$?

Question

What does this notation mean $\{a_k\}_{k=i}^n$?

I saw it in sites talking about sequences but there was no explanation of what it meant.

E: I reviewed the other post, this is not a duplicate, and the chosen answer described what I asked.

Answer 1

${\{a_k\}}_{k=i}^n$ means the list of terms in the sequence $a_k$, ranging from $k=i$ to $k=n$; i.e.:

$$a_i,a_{i+1},a_{i+2},...,a_n$$

Answer 2

It means the following collection of objects: $$\{a_k\}_{k=i}^n=\left \{ a_i,a_{i+1},a_{i+2},\dots,a_n \right \}$$

• For example, if $i=1$ and $n=5$, we would have: $$\{a_k\}_{k=1}^5=\left \{ a_1,a_{2},a_{3},a_{4},a_5 \right \}$$