PhpSpreadsheet/tests/data/ColumnIndex.php

<?php

return [
    [
        0,
        'A',
    ],
    [
        25,
        'Z',
    ],
    [
        26,
        'AA',
    ],
    [
        27,
        'AB',
    ],
    [
        51,
        'AZ',
    ],
    [
        52,
        'BA',
    ],
    [
        77,
        'BZ',
    ],
    [
        78,
        'CA',
    ],
    [
        255,
        'IV',
    ],
    [
        701,
        'ZZ',
    ],
    [
        702,
        'AAA',
    ],
    [
        1378,
        'BAA',
    ],
];