\mathellipsis
The \mathellipsis command in LaTeX is used to produce an ellipsis (three dots) in mathematical mode. It is typically used to indicate the continuation of a sequence or series in mathematical expressions.
Indicating a sequence of terms in a series.
a_1, a_2, \mathellipsis, a_n
Representing the sum of a series of numbers.
1 + 2 + \mathellipsis + n
Denoting a product of a sequence of variables.
x_1 x_2 \mathellipsis x_n