23.亲密数

 代码实现：

#include<stdio.h>
void main(){

int a,i,b,n;
printf("There are following friendly-numbers pair smaller than 3000:\n");
for(a=1;a<3000;a++){
for(b=0,i=1;i<=a/2;i++)
if(!(a%i))
b+=i;
for(n=0,i=1;i<=b/2;i++)
if(!(b%i))
n+=i;
if(n==a&&a<b)
printf("%4d--%4d\n",a,b);
}

}