C "for"循环问题

Question

我正在运行这个程序

#include <stdio.h>
int main ()
{
  int n;
  int a = 1;
  int b = 2;
  int product;
  int i;

  printf("How many numbers of the sequence would you like \n");
  scanf("%d",&n);

  for (i=0;i<n;i++)
  {
    printf("%d\n",a);
    product = a * b;
    a = b;
    b = product;
  }

   return 0;
}

当我输入 n = 3 时，结果是 1 2 2
为什么 ？我打算让它显示 1 2 4，我做错了什么？为什么打印 1 2 2 。

Answer 1

And why is it print 1 2 2 .

printf("%d\n",a); 的逐步跟踪:

i  a  b  product
0  1  2  ?
1  2  2  2
2  2  4  4
3  4  8  8
4  8  32 32