Question

Write a recursive formula for 16, 9, 7, 2, 5

Answer 1

Notice that:

7=16-9
2=9-7
5=7-2

the next term would be: 2-5=-3

so each term of the sequence is equal to its previous term, subtracted from the second previous term:

Also, in order to describe the formula, we need to express the 2 first terms, 1 is not enough.

The recursive formula is:

$a_1=16$
$a_2=9$
 $a_n_2=a_n_1-a_n$