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What is the difference between a sequence and a series?

Published in Math Concepts 2 mins read

A sequence is an ordered list of numbers, while a series is the sum of the terms in a sequence.

Here's a more detailed breakdown:

Sequences

  • Definition: A sequence is an arrangement of numbers in a particular order, as stated in the reference. Each number in the sequence is called a term.
  • Examples:
    • Arithmetic Sequence: 2, 4, 6, 8, 10... (Each term increases by a constant difference)
    • Geometric Sequence: 3, 9, 27, 81... (Each term is multiplied by a constant ratio)
    • Fibonacci Sequence: 1, 1, 2, 3, 5, 8... (Each term is the sum of the two preceding terms)
  • Key Characteristic: Order is critical in a sequence; changing the order creates a different sequence.

Series

  • Definition: A series is the sum of the elements of a sequence, according to the reference. You obtain a series by adding up all the terms in a sequence.
  • Examples:
    • Arithmetic Series: 2 + 4 + 6 + 8 + 10 + ... (Sum of the arithmetic sequence)
    • Geometric Series: 3 + 9 + 27 + 81 + ... (Sum of the geometric sequence)
    • Fibonacci Series: 1 + 1 + 2 + 3 + 5 + 8 + ... (Sum of the Fibonacci sequence)
  • Key Characteristic: A series is a result of an addition operation on a sequence.
  • Convergence: One of the important characteristics of series is whether they converge to a finite value or not.

Table Summarizing Differences

Feature Sequence Series
Definition An ordered list of numbers. The sum of terms in a sequence.
Operation Represents the order, not a sum. Represents an addition operation.
Key Feature Maintaining order is crucial. Represents a calculation resulting in a sum.
Representation Terms separated by commas. Terms separated by addition signs.
Example 1, 2, 3, 4, 5... 1 + 2 + 3 + 4 + 5 + ...

Practical Insights

  • Understanding the difference between sequences and series is fundamental in calculus, particularly when dealing with infinite processes.
  • Sequences can be finite or infinite, and the same applies to the length of the terms used to form the series
  • Series analysis involves determining if the sum converges to a finite value or diverges (approaches infinity)

In essence, a sequence lays out a pattern, while a series quantifies the total that arises from the pattern of numbers in a sequence through addition.

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