My goal here is to define the function doublefactorial. The domain of this function is the set of positive integers. For a positive even integer n the value of DoubleF[n] is the product of all positive even integers which are <=n. For a positive odd integer n the value DoubleF[n] is the product of all positive odd integers which are<=n.
I want to make a recursive definition of this function but do not know how. Here is some code so far:
MyF1 = 1;
MyF1[n_Integer] /; (n > 0) := MyF1[n] = n*MyF1[n - 1]