+808 Double factorial (aka semifactorial) is a mathematical operation in which one multiplies "every other" natural number up to a given number. A more precise definition is:
$$n!!=\prod \limits_{i=0}^{k}(n-2i)= n(n-2)(n-4)(n-6)...$$
Where k = (n/2) - 1
Or read more on the "Double Factorial" Wikipedia web page :)
+808 How about:
4 + √4 +√4 +√4
Technically speaking you've used two's since √x = 2√x
+808 Double factorial (aka semifactorial) is a mathematical operation in which one multiplies "every other" natural number up to a given number. A more precise definition is:
$$n!!=\prod \limits_{i=0}^{k}(n-2i)= n(n-2)(n-4)(n-6)...$$
Where k = (n/2) - 1
Or read more on the "Double Factorial" Wikipedia web page :)
