用C语言的递归输出一个99乘法表，请问怎么实现。不能用循环实现

用C语言的递归输出一个99乘法表，请问怎么实现。不能用循环实现，请问怎么做

 #include <stdio.h>

void foo(int acc1, int acc2)
{
    if (acc1 > 9) return;
    printf("%d * %d = %d\t", acc1, acc2, acc1 * acc2);
    if (acc2 >= acc1) { acc2 = 1; acc1++; printf("\n"); } else { acc2++; }
    foo(acc1, acc2);
}

int main()
{
    foo(1, 1);
}

 1 * 1 = 1  
2 * 1 = 2   2 * 2 = 4   
3 * 1 = 3   3 * 2 = 6   3 * 3 = 9   
4 * 1 = 4   4 * 2 = 8   4 * 3 = 12  4 * 4 = 16  
5 * 1 = 5   5 * 2 = 10  5 * 3 = 15  5 * 4 = 20  5 * 5 = 25  
6 * 1 = 6   6 * 2 = 12  6 * 3 = 18  6 * 4 = 24  6 * 5 = 30  6 * 6 = 36  
7 * 1 = 7   7 * 2 = 14  7 * 3 = 21  7 * 4 = 28  7 * 5 = 35  7 * 6 = 42  7 * 7 = 49  
8 * 1 = 8   8 * 2 = 16  8 * 3 = 24  8 * 4 = 32  8 * 5 = 40  8 * 6 = 48  8 * 7 = 56  8 * 8 = 64  
9 * 1 = 9   9 * 2 = 18  9 * 3 = 27  9 * 4 = 36  9 * 5 = 45  9 * 6 = 54  9 * 7 = 63  9 * 8 = 72  9 * 9 = 81

你先学习下循环是怎么实现的吧