Problem 292. Infernal Recursion

Consider the recursion relation:

x_n = (x_(n-1)*x_(n-2))^k

Given x_1, x_2, and k, x_n can be found by this definition. Write a function which takes as input arguments x_1, x_2, n and k. The output should be x_n.

For example, if x_1=exp(1), x_2=pi, n=5, and k=5/9 then:

R = get_recurse(exp(1),pi,5,4/9)

R =
      2.31187497992966