| public testLahNumberIdentityKEqualsTwo ( integer $n ) | ||
| $n | integer | |
public function testLahNumberIdentityKEqualsTwo(int $n)
{
// Skip exception where n < k
if ($n === 1) {
return;
}
$L⟮n、1⟯ = Combinatorics::lahNumber($n, 2);
$⟮n−1⟯n！／2 = ($n - 1) * Combinatorics::factorial($n) / 2;
$this->assertEquals($L⟮n、1⟯, $⟮n−1⟯n！／2);
}