What number should replace the question mark in 2, 7, 22, ?, 202, 607?

Explanation

1. 01

   Test $\times 3 + 1$ on the known terms: $2 \times 3 + 1 = 7$, $7 \times 3 + 1 = 22$.

2. 02

   So the missing term is $22 \times 3 + 1 = 67$.

3. 03

   Check it forward: $67 \times 3 + 1 = 202$ and $202 \times 3 + 1 = 607$.