Double factorial facts for kids

Kids Encyclopedia Facts

Double factorial is a method of calculating how many times a number is repeated in a geometric equation. This way, we can calculate the number of times a product is used in its life-time.

The double factorial of n is written as $n!!$ . When n is a positive odd integer, $n!!$ is defined as $n \cdot (n-2) \cdot\, \cdots \, \cdot 3 \cdot 1$ . When n is an positive even integer, $n!!$ is defined as $n \cdot (n-2) \cdot\, \cdots \, \cdot 4 \cdot 2$ . By definition, $0!! = 1$ .

Factorial
Permutation

Double factorial facts for kids

Related pages

See also