a function that generate and return count of how many subsequences of an array

subsequence.cpp

#include <iostream>
#include <math.h>


int subsequence (int arr[],int length)
{
    int counter = 0;
    // how many times iterate (extend from this formula => 2^n - 1)
    int power = pow(2, length);

    for(size_t i = 1; i < power; i++) 
    {
        std::cout << '[';
        for(size_t j = 0; j < length; j++)
        {
            if(i & ( 1 << j))
            {
                std::cout << arr[j] << ',';
                
            }

        }
        std::cout << ']' << std::endl;
    }
    return power - 1;
}

int main()
{
    int arr[] = { 1, 2, 3, 4};
    int length = sizeof(arr) / sizeof(*arr);

    std::cout << subsequence(arr, length);


    return 0;
};