Show that the sequence defined by `a_n=2n^2+1` is not an A.P.

Explanation

To show that the sequence defined by \( a_n = 2n^2 + 1 \) is not an arithmetic progression (A.P.), we need to check if the difference between consecutive terms is constant.

### Step-by-Step Solution:

1. **Calculate the first three terms of the sequence:**
- For \( n = 1 \):
\[
a_1 = 2(1)^2 + 1 = 2 \cdot 1 + 1 = 2 + 1 = 3
...