Notice that the pattern of the data set is the previous term plus 4. This is an arithmetic sequence where the difference (d) is +4.
= a₁ + d(n - 1) ; where a₁ is the first term, d is the difference, and n is the term.
= 12 + 4(n - 1)
= 12 + 4n - 4
= 4n + 8