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Theory:

A sequence is a function defined on the set of natural numbers \(\mathbb{N}\). A sequence is a function of form f:, where \(\mathbb{R}\) is the set of all real numbers.
If the sequence is of the form  \(a_1\), \(a_2\), \(a_3\), \(a_4\), ... then we can associate the function to the sequence \(a_1\), \(a_2\), \(a_3\), \(a_4\), ... by \(f (n) = a_n\), \(n = 1, 2, 3,\) …
 
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Let us solve a problem of sequence with a function to understand this concept.
Example:
The general term of a sequence is defined as f(n)=an=2n+4n+7. Find the first three terms \(a_1\), \(a_2\), a3.
 
Let us substitute the natural number \(n = 1, 2, 3, 4, ...\) in the given equation.
 
The first three terms are:
 
f(n)=an=2n+4n+7, where \(n = 1, 2, 3, 4, ...\)
 
a1=2(1)+41+7
 
=2+48
 
a1=68
 
a2=2(2)+42+7
 
=4+49
 
a2=89
 
a3=2(3)+43+7
 
=6+410
 
a3=1010
 
Therefore, the first three terms are 68, 89 and 1010.