What will come at the place of question mark ? 2, 3, 6, 15, ?, 123

47
42
45
50

The answer is 42.

The sequence is $a_n = 3a_{n-1} – a_{n-2}$, with $a_0 = 2$ and $a_1 = 3$. This means that each term is the sum of the two terms before it, except for the first two terms, which are 2 and 3.

To see this, we can write out the first few terms of the sequence:

$a_0 = 2$
$a_1 = 3$
$a_2 = 3 \cdot 2 – 3 = 3$
$a_3 = 3 \cdot 3 – 2 = 6$
$a_4 = 3 \cdot 6 – 3 = 15$
$a_5 = 3 \cdot 15 – 6 = 42$

Therefore, the answer is 42.

Option A, 47, is incorrect because it is not in the sequence.

Option B, 42, is correct because it is the fifth term in the sequence.

Option C, 45, is incorrect because it is not in the sequence.

Option D, 50, is incorrect because it is not in the sequence.