Step 1: Analyze the number sequence:
\[
2, 6, 12, 20, 30, 42, 56
\]
Step 2: The numbers follow the formula \( n(n+1) \) for \( n = 1, 2, 3, \ldots \). Verify each term:
\[
1 \times 2 = 2, \quad 2 \times 3 = 6, \quad 3 \times 4 = 12, \quad 4 \times 5 = 20, \quad 5 \times 6 = 30, \quad 6 \times 7 = 42, \quad 7 \times 8 = 56
\]
Step 3: Examine divisibility by 3. Numbers 6, 12, 30, and 42 are divisible by 3. Numbers 2 and 56 are not. As 2 is not an outlier in the given options, 56 is the odd one out because it is not divisible by 3, unlike the other numbers in the sequence.