CBSE (Arts) Class 11CBSE
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Concept of Sequences

notes

Let us consider the following examples: Assume that there is a generation gap of 30 years, we are asked to find the number of ancestors, i.e., parents, grandparents, great grandparents, etc. that a person might have over 300 years.
Here, the total number of generations = 300 /30 =10
The number of person’s ancestors for the first, second, third, …, tenth generations are 2, 4, 8, 16, 32, …, 1024. These numbers form what we call a sequence.
The n^(th) term is the number at the nth position of the sequence tand is denoted by a^n.The n^(th) term is also called the general term of the sequence.
A sequence containing finite number of terms is called a finite sequence. For example, sequence of ancestors is a finite sequence since it contains 10 terms (a fixed number).
A sequence is called infinite, if it is not a finite sequence.  For example, the sequence of successive quotients mentioned above is an infinite sequence, infinite in the sense that it never ends.
a sequence can be regarded as a function whose domain is the set of natural numbers or some subset of it. Sometimes, we use the functional notation a(n) for a_n.

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