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Sequence

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A sequence is an ordered list of terms. Sequences may be either finite or infinite.

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Definition

A sequence of real numbers is simply a function f : \mathbb{N} \rightarrow \mathbb{R}. For instance, the function f(x) = x^2 defined on \mathbb{N} corresponds to the sequence X = (x_n) = (0, 1, 4, 9, 16, \ldots).

Convergence

Intuitively, a sequence converges if its terms approach a particular number.

Formally, a sequence (x_n) of reals converges to L \in \mathbb{R} if and only if for all positive reals \epsilon, there exists a positive integer k such that for all integers n \ge k, we have |x_n - L| < \epsilon.

If (x_n) converges to L, L is called the limit of (x_n) and is written \lim_{n \to \infty} x_n.

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