(possibly the earliest publication to use double factorial notation) states that the double factorial was originally introduced in order to simplify the expression of certain trigonometric integrals arise in the derivation of the Wallis merchandise. The term odd factorial is sometimes used for the double factorial of an odd number.

COMING SOON!

```
package main
import "fmt"
func factorial(num int) int {
if num == 0 {
return 1
}
return num * factorial(num - 1)
}
func main() {
num := 10
result := factorial(num)
fmt.Println(result)
}
```