(2 × 1 + 1) × 3 = 9
(2×2+1) × 3 = 15
(2×3+1) × 3 = 21
(2×4+1) × 3 =27
(2×5+1) × 3 = 33
(2×6+1) × 3 = 39
(2 × 1 + 1) × 3 = 9
(2×2+1) × 3 = 15
(2×3+1) × 3 = 21
(2×4+1) × 3 =27
(2×5+1) × 3 = 33
(2×6+1) × 3 = 39