Powerful Integers

import math
class Solution(object):
    def powerfulIntegers(self, x, y, bound):
        pow = []
        x1 = int(math.log(bound, x)) if x!=1 else 1
        y1 = int(math.log(bound, y)) if y!=1 else 1
        for i in range(x1+1):
        	for j in range(y1+1):
        		if x**i+y**j <= bound:
        			if x**i+y**j not in pow:
        				pow.append(x**i+y**j)
        return pow