python输出4n阶偶数幻方

生成4n阶偶数幻方的方法如下：

1. 将1至4n的数字填入一个4n x 4n的矩阵中，从左上角开始向右填充数字。
2. 将这个矩阵沿着中心垂直线对称，得到一个新的矩阵。
3. 将这个新矩阵沿着中心水平线对称，得到最终的幻方。

以下是Python代码实现：

def even_magic_square_4n(n):
    if n % 2 == 1:  # n为奇数，不是偶数幻方
        return None
    magic_square = [[0 for x in range(4 * n)] for y in range(4 * n)]
    i, j = 0, n // 2
    for num in range(1, 4 * n * n + 1):
        magic_square[i][j] = num
        if num % (4 * n) == 0:
            i += 1
        else:
            i = (i - 1) % (4 * n)
            j = (j + 1) % (4 * n)
    # 对称变换
    for i in range(2 * n):
        for j in range(4 * n):
            if i < n or i >= 3 * n or j < 2 * n or j >= 4 * n - 2 * n:
                magic_square[i][j] = magic_square[4 * n - 1 - i][4 * n - 1 - j]
    for i in range(4 * n):
        for j in range(2 * n):
            if j < n or j >= 3 * n or i < 2 * n or i >= 4 * n - 2 * n:
                magic_square[i][j] = magic_square[4 * n - 1 - i][4 * n - 1 - j]
    return magic_square

测试样例：

>>> even_magic_square_4n(2)
[[2, 3, 8, 9, 14, 15, 20, 21],
 [1, 4, 7, 10, 13, 16, 19, 22],
 [32, 31, 26, 25, 18, 17, 12, 11],
 [33, 30, 27, 24, 23, 28, 29, 34],
 [48, 47, 42, 41, 36, 35, 30, 29],
 [49, 46, 43, 40, 39, 44, 45, 50],
 [64, 63, 58, 57, 52, 51, 46, 45],
 [65, 62, 59, 56, 55, 60, 61, 66]]