Math 2.0

Sequences, series, summability Definition

Series

Builds on Real sequence

Definition

Let (an)n∈ℕ(a_n)_{n \in \mathbb{N}} be a real sequence. The series with terms ana_n is the sequence (sN)N∈ℕ(s_N)_{N \in \mathbb{N}} given by sN=a0+a1+⋯+aN=∑n=0Nan.s_N = a_0 + a_1 + \cdots + a_N = \sum_{n=0}^{N} a_n. The notation for the series is ∑n=0∞an\sum_{n=0}^{\infty} a_n, or ∑an\sum a_n.

Remarks

The number sNs_N is a partial sum of the series. The symbol ∑n=0∞an\sum_{n=0}^{\infty} a_n also denotes the sum of the series, when the series is convergent. The context shows which meaning is intended. A series can start at another index, for example ∑n=1∞1/n\sum_{n=1}^{\infty} 1/n.

Reading path

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  1. Sequence definition
  2. Real sequence definition
  3. Series definition

Where this leads

243 pages build on this one.

Further reading

  1. Web https://en.wikipedia.org/wiki/Series_(mathematics), Definition
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