#include <bits/stdc++.h>

using namespace std;

long long s,i,n;

int main()

{

cin>>n;

s=0;

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

if (i%2==1) s=s+i*i;

cout<<s;

return 0;

}

Bạn nêu rõ dữ liệu vào nhé

Code c:

#include <stdio.h>

#include <conio.h>

#include <math.h>

#define PI 3.14159

int main() {

            int r;

            float chuvi, dientich;

            printf("Nhap ban kinh r:");

            scanf("%d", &r);

            chuvi = 2*PI*r;

            dientich = PI*r*r;

            printf("Chu vi hinh tron la: %f\n", chuvi);

            printf("Dien tich hinh tron la: %f", dientich);

            getch();

BN THAM KHẢO:

Program S_Hinh_Tron;
Uses Crt;
Var r,S:real;
Begin
Clrscr;
Writeln(‘TINH DIEN TICH HINH TRON:’);
Write (‘Nhap ban kinh R=’);readln(r);
dt:=pi*r*r;
Writeln(‘Dien tich hinh tron la:’,dt:6:2);
Readln;
End.

Var a:array[1..200] of real;

i,n,dem:integer;

s,tbc:real;

Begin

Write('Nhap so luong phan tu n = ');readln(n);

s:=0;

For i:=1 to n do

Begin

Write('Nhap phan tu thu ',i,' = ');readln(a[i]);

s:=s+a[i];

End;

tbc:=s/n;

Write('Trung binh cong la ',tbc:10:2);

Readln;

End.

Bài 2: 

#include <bits/stdc++.h>
using namespace std;
long long n,i;
//chuongtrinhcon
int demuoc(long long n)
{
    int dem=0;
    for (long long i=1; i<=n; i++)
        if (n%i==0) dem++;
    return (dem);
}
//chuongtrinhchinh
int main()
{
    freopen("tamuoc.inp","r",stdin);
    freopen("tamuoc.out","w",stdout);
    cin>>n;
    long long dem=0;
    for (i=1; i<=n; i++)
        if (demuoc(i)==3) dem++;
    cout<<dem;
    return 0;
}

1.

#include <bits/stdc++.h>

using namespace std;

int A,n,i;

int main()

{

cin>>n;

A=0;

For (i=0;i<=n;i++)

A=A+1/i;

cout<<A;

Return 0;

}