## 2015-10-26

### Double Factorial Table

The double factorial is the product of a number and every second natural number less than itself. That is:

$$n!! = \prod_{k = 0}^{ \lceil n/2 \rceil - 1} (n - 2k) = n(n-2)(n-4)...$$

Presentation of the values for double factorials is usually split up into separate even- and odd- sequences. Instead, I wanted to see the sequence all together, as below: