Double Factorial Calculator

Double factorial calculator calculates the double factorial of a given number.

Double Factorial Formula

what is double factorial?
The double factorial is similar to the factorial, except for the decrement by 2 instead of the decrement by 1.

The double factorial formula is:
n!!=n x (n-2) x (n-4) x (n-6) x (n-8)...x 1 (for odd integer)
n!!=n x (n-2) x (n-4) x (n-6) x (n-8)...x 2 (for even integer)

For example,
for an even integer, it is calculated as:
12!! = 12 x 10 x 8 x 6 x 4 x 2= 46,080

For an odd integer, it is calculated as:
9!! = 9 x 7 x 5 x 3 x 1= 945