Definition:Subsequence/Warning

Definition

In the definition of a subsequence, the constraint that $\sequence {n_r}$ be strictly increasing is important.

Thus, for example, $x_3, x_1, x_4, x_2, x_9, x_5 \ldots$ is not a subsequence of $\sequence {x_n}$.

Sources

• 1977: K.G. Binmore: Mathematical Analysis: A Straightforward Approach ... (previous) ... (next): $\S 5$: Subsequences: $\S 5.1$: Subsequences