1, 2, 6, 7, 21, 22, 66, 67,?

Each term in the series, except the first two terms, is the product of the preceding two terms.

So, missing term = 16 x 128 = 2048.

Each term in the series is obtained by subtracting from the preceding term the number

formed by the first three digits of the preceding term.

So, missing term = 5242 - 524 = 4718.

The pattern is + 1008.

So, missing term - 6848 + 1008 = 7856.

Let the missing terms of the series be x₁ and x₂.

Thus, the sequence 2, 15, 4, 12, 6, 7, x₁ x₂ is a combination of two series :

I. 2, 4, 6, x₁ and II. 15, 12, 7, x₂I consists of consecutive even numbers.

So, missing term, x₁ = 8.

The pattern in II is - 3, - 5,......So, missing term, x₂ = 7 - 7 = 0.

The pattern is x 1, x 2, x 3, x 4,.....

So, missing term = 24 x 5 = 120.

The pattern is + 0.05, + 0.10, + 0.15,.....

So, missing term = 0.8 + 0.20 = 1.

The given sequence is a combination of two series :

I. 0, 3, 8, 15, 24, ? and II. 2, 5, 10, 17, 26

The pattern in each one of I and II is + 3, + 5, + 7, + 9, .....

So, missing term = 24 + 11 = 35.

The pattern is + 2, + 4, + 2, + 4, .....

So, missing term = 25 + 4 = 29.

Each term in the series, except the first two terms, is the sum of the preceding two

terms.

So, missing term = 16 + 25 = 41.

The terms of the given series are (2³ - 1), (3³ - 1), (4³ - 1), (5³ - 1), (6³ - 1), (7³ - 1),.....

So, missing term = (8³ - 1) = (512 - 1) = 511.