Collatz conjecture's sequence of numbers

collatz.php

<?php

declare(strict_types=1);

include 'vendor/autoload.php';

use drupol\collection\Collection;

// The Collatz conjecture (https://en.wikipedia.org/wiki/Collatz_conjecture)
$collatz = static function (int $initial = 1): int
{
    return 0 === $initial % 2 ?
        $initial / 2:
        $initial * 3 + 1;
};

Collection::iterate($collatz, 10)
    ->until(static function ($number): bool {
        return 1 === $number;
    })
    ->all(); // [5, 16, 8, 4, 2, 1]