Correct. Each term is 3 more than the previous term. If the sequence was simply $\displaystyle{3}{n}\usepackage{cmbright}\Huge\$ , then the sequence would have gone 3, 6, 9, 12, 15; subtracting 1 from each term is necessary. The correct sequence is $\displaystyle{3}{n}-{1}\usepackage{cmbright}\Huge\$ .