Power of Three
Given an integer, write a function to determine if it is a power of three.

Follow up:
Could you do it without using any loop / recursion?

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var NumArray = function(nums) {
    nums = [-2, 0, 3, -5, 2, -1];
};
NumArray.prototype.sumRange = function(i, j) {
    //var nums = [-2, 0, 3, -5, 2, -1];
    var sum=0;
        for(var k=i;k<j;k++){
            sum+=NumArray[k];
        }
        return sum;
};