分子分母有关系的序列和.c

#include<stdio.h>

int main()

{ int i,n;

double sum=0,x1,x2,x;

scanf("%d",&n);

x1=2;

x2=1;

for(i=1;i<=n;i++){

sum+=x1/x2;

x=x1;

x1=x1+x2;

x2=x;

}

printf("%.2f\n",sum);

return 0;

}