http://acm.pku.edu.cn/JudgeOnline/problem?id=1218

Код:
#include <stdio.h>

int main()
{
    int T,n;
    int i,j;

    scanf("%d", &T);
    while(T--) {
        int cnt=0;
        int cell[101]={0,};
        scanf("%d", &n);

        for(i=1;i<=n;i++) {
            for(j=i;j<=n;j+=i) {
                cell[j] = !cell[j];
            }
        }

        for(i=1;i<=n;i++)
            if(cell[i]) cnt++;

        printf("%d\n", cnt);
    }

    return 0;
}