Wallis's Formula

Use the Wallis's formula to find the the approximate value of pi.

Use the following "Wallis's formula" to find the the approximate value of pi.

π = 2･{(2･2･4･4･6･6･8･8･･･)/(1･3･3･5･5･7･7･9･･･)}

Let's observe how the approximate value of pi can be obtained as the number of numerator and denominator numbers increases.