Recurance Relations

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A sequence is sometimes defined by a recurrence relation. This tells you how to find the next term, given the current term.

For example:

This tells you that the first term is 2.

To find the next term you add 2

This gives the sequence
A second example To generate each term, you double the previous term, then add 1.
This gives

The rule could refer to more than one of the previous terms, such as This says that to generate each term, you add the previous 2 terms together. Obviously you need to be given 2 starting terms.
This gives the famous Fibonacce series

A recurrence relation can give a convergent sequence Each term is half the previous term.
This gives

A recurrence relation can also give an oscillating sequence. To generate each term, subtract the previous term from 1.
This gives

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