Untitled

<script language="JavaScript">
function genCode() {
 var serial = document.getElementById('serial').value;
 var code = (27182 * (serial % 1000) + 247290789) ^ 693147180;
 document.getElementById('code').value = code;
}
</script>

Serial Number: <input type=text name="serial" size=10 id="serial">
<input type=button onclick="genCode();" value="Generate Code"><br>
Code: <input type=text name="code" size=10 id="code">