Two sequences where the second sequence can be found by multiplying each term in the first sequence by the same number are proportional sequences.

- This number is called the coefficient of proportionality.
- The relationship of a term in the first sequence and the term in the same rank in the second sequence is called the proportionality constant or the proportionality relationship.

### Example

The sequences *s _{1}* = {1, 1, 2, 3, 5, 8, 13, 21, …} and

*s*= {2, 2, 4, 6, 10, 16, 26, 42, …} are proportional because we find the second by multiplying each term in the first sequence by 2.

_{2}The coefficient of proportionality between these two sequences is 2. The proportionality constant is \(\frac{1}{2}\).