We have, an = n (n + 2)
Substituting n = 1, 2, 3, 4, 5, we get
a1 = 1 (1 + 2) = 1 × 3 = 3
a2 = 2 (2 + 2) = 2 × 4 = 8
a3 = 3 (3 + 2) = 3 × 5 = 15
a4 = 4 (4 + 2) = 4 × 6 = 24
a5 = 5 (5 + 2) = 5 × 7 = 35
∴ The first five terms are 3, 8, 15, 24 , 35.