------
## 最终结论
```python
def sum_even_and_even_index(numbers, n):
    total = 0
    for index, value in enumerate(numbers):
        if index % 2 == 0 and value % 2 == 0:
            total += value
    return total

# Test cases
assert sum_even_and_even_index([5, 6, 12, 1, 18, 8],6) == 30
assert sum_even_and_even_index([3, 20, 17, 9, 2, 10, 18, 13, 6, 18],10) == 26
assert sum_even_and_even_index([5, 6, 12, 1],4) == 12
```