A punctuation symbol showing three horizontally centered dots to indicate omission or continuation in mathematical expressions.
Examples
Sequence continuation
1, 2, 3, \mathellipsis, n
Matrix elements
A = \begin{pmatrix} a_{11} & a_{12} & \mathellipsis & a_{1n} \\ a_{21} & a_{22} & \mathellipsis & a_{2n} \end{pmatrix}
Series summation
\sum_{i=1}^n x_i = x_1 + x_2 + \mathellipsis + x_n