How to print this series 1 2 3 6 9 18 27 54 ... in C language

This series 1 2 3 6 9 18 27 54 has a pattern. The pattern is for odd position it adds up the previous number. For even position it doubles the number. Following is the implementation in C language:

#include 

int main()
{
    int sum = 1, last = 0;
    for(int i = 1; i < 10; i++){
        if(i % 2 == 0) {
            last = sum;
            sum *=2;
        } else {
            sum +=last;
        }
        printf("%d ", sum);
    }
    
    return 0;
}