C++ :

#include <bits/stdc++.h>
using namespace std;

int main(){
	int i,j,n,a[20][20] = {0},t=1;
	cin>>n;
	for(i = 0;i< n;i++){
		for(j = 0;j < n - i;j++){
			a[j][j+i] = t;
			a[j+i][j] = t;
			t++;
		}
	}
	
	for(i = 0;i < n;i++){
		for(j = 0;j < n;j++){
			cout<<setw(5)<<a[i][j];
		}
		cout<<endl;
	}
    return 0;
}

Python :

n = int(input())
a = [[0 for j in range(n)] for i in range(n)]
m = 1
# k认为是左对角线的偏移量
for k in range(n):
    # i为从上到下的坐标
    for i in range(0, n - k):
        a[i][k + i] = m
        a[k + i][i] = m
        m += 1

# 打印输出
for i in range(n):
    for j in range(n):
        print('%5d' % a[i][j], end='')
    print()