an / 2 – 1 = an+1
1: #include <stdio.h>
2:
3: int main()
4: {
5: int sum = 1, i;
6: for (i = 9; i >= 1; i--)
7: {
8: sum = (sum + 1) * 2;
9: }
10: printf("the num of peace are %d\n", sum);
11: return 0;
12: }