Rule that we identify in a sequence of numbers or images, when a term in the sequence (number or sign) can be deduced from the other terms in the sequence.

Phenomenon that we find in arithmetic sequences, geometric sequences or arrangements of figures when a term in the sequence (number or figure) can be deduced from a rule.

### Examples

Some sequences are numerical, such as arithmetic and geometric sequences.

- The rule of the arithmetic sequence 3, 5, 7, 9, 11, 13, … is (
*n*+ 2) where n is the*n*-th term in the sequence. - The rule of the geometric sequence 1, 3, 9, 27, 81, 243, … is 3
*n*where*n*is the*n*-th term in the sequence.

Other sequences are not numerical, such as arrangements of figures or sequences of figures.

- Arrangement of figures: