牛牛学数列3
牛牛学数列3
http://www.nowcoder.com/questionTerminal/f65c726d081c4160a9356eabf0dc21d9
include<stdio.h>
main()
{int n,i,k=1,sum=0,sign=1;
double m=0.0;
scanf("%d",&n);
for(i=1;i<=n;i++)
{sum=sum+sign*(2*k-1);
m+=1.0/sum;
sign*=-1;
k++;}
printf("%.3lf",m);}
）