<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
<?php
for ($i=20; $i>1; $i=$i-2){
$kwadraat = $i*$i;
echo"Het kwadraat van $i = $kwadraat. <br/>";
}
?>
</body>
</html>