Subsequence

In mathematics, a subsequence is a sequence that can be derived from another sequence by deleting some elements without changing the order of the remaining elements. For example, the sequence ${\displaystyle \langle A,B,D\rangle }$ is a subsequence of ${\displaystyle \langle A,B,C,D,E,F\rangle }$ obtained after removal of elements ${\displaystyle C}$, ${\displaystyle E}$, and ${\displaystyle F}$. The relation of one sequence being the subsequence of another is a preorder.

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