Since the difference between consecutive terms is not constant, the sequence is not arithmetic.
In an arithmetic sequence, the difference between consecutive terms is constant, called common difference d.
A recursive formula is given by:
[tex]a_{n+1} = a_{n} + d[/tex]
In which [tex]a_1[/tex] is the first term.
In this problem:
A similar problem is given at https://brainly.com/question/23901992