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Sequences

Numerical Sequence

Definition Numerical Sequence
A numerical sequence is an ordered list of numbers \((u_0,\,u_1,\,u_2,\dots)\) defined by a rule.
\(n\) 0 1 2 \(\dots\)
\(u_n\) \(u_0\) \(u_1\) \(u_2\) \(\dots\)
The number \(u_n\) is called the \(n\)th term of the sequence.
Example
What is \(u_4\) of this sequence?
\(n\) 0 1 2 3 4 5 \(\dots\)
\(u_n\) 3 5 7 9 11 13 \(\dots\)

\(u_4 = 11\).

Definition Using a Recursive Rule

Definition Recursive Rule
A sequence can be defined by:
  • the first term (starting number), and
  • a recursive rule that tells how to obtain each term from the previous one.
Example
Write the sequence defined by: the first term is \(2\), and each term is obtained by adding \(3\) to the previous term.