参考答案：

#include<iostream>

using namespace std;

int main()
{
    int a;
    int k = 1;

    cin >> a;
    for (int i = 1; i <= a; ++i)
    {
        for (int j = 1; j <= i; ++j)
        {
            printf("%-4d", k ++);
        }
        cout << endl;
    }

    return 0;
}

Python:

a = int(input())
num = 0
for i in range(1,a+1):
    for j in range(1,i+1):
        num += 1
        print(str(num).ljust(4), end='')
    print()