$\"\"$

Observe the figure:

Let the rows are $\"\"$ .

The columns are $\"\"$ .

The total stars in the figure is $\"\"$ .

The stars on the left side is $\"\"$ .

The stars on the right side is $\"\"$ .

The total stars are $\"\"$ .

$\"\"$

$\"\"$ .

The formula $\"\"$ is valid for all positive integers $\"\"$ . $\"\"$

The formula $\"\"$ is valid for all positive integers $\"\"$ .