\ldots
Ellipsis, used to indicate continuation or omission in mathematical expressions or text.
Indicating a sequence of numbers from 1 to n.
1, 2, 3, \ldots, n
Summation of a series of terms.
a_1 + a_2 + \ldots + a_n
List of variables or elements in a set.
x_1, x_2, \ldots, x_n