1. **State the problem:** We are given the sequence 2, 6, 12, 20, 30 and asked to analyze it.
2. **Identify the pattern:** Notice the terms: 2, 6, 12, 20, 30.
3. **Check if the terms fit a formula:** Let's try to express the $n$th term $a_n$ in terms of $n$.
4. **Calculate the terms with $n=1,2,3,4,5$:**
- $a_1 = 2$
- $a_2 = 6$
- $a_3 = 12$
- $a_4 = 20$
- $a_5 = 30$
5. **Try the formula $a_n = n(n+1)$:**
- For $n=1$, $1 \times 2 = 2$ ✓
- For $n=2$, $2 \times 3 = 6$ ✓
- For $n=3$, $3 \times 4 = 12$ ✓
- For $n=4$, $4 \times 5 = 20$ ✓
- For $n=5$, $5 \times 6 = 30$ ✓
6. **Conclusion:** The $n$th term of the sequence is given by the formula
$$a_n = n(n+1)$$
This means each term is the product of $n$ and its successor $n+1$.
7. **Additional insight:** This sequence represents the sequence of pronic numbers, which are the product of two consecutive integers.
**Final answer:** The formula for the sequence is $a_n = n(n+1)$.
Pronic Numbers
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