Arithmetic & Number Theory
Double Factorial
Product of integers with the same parity down to 1.
Formula
Formula
n!! = n(n−2)(n−4)⋯
Variables
| Symbol | Definition | Type & range | Units | Role |
|---|---|---|---|---|
| n | non-negative integer | integer (ℤ) | — | input |
| n!! | double factorial | integer (ℤ) | — | input |
Try it yourself
Interactive calculator
Worked examples
Example 1
Givenn = 9
Result945
Example 2
Givenn = 8
Result384