[ваый]

<table>
<tr>
    <td></td>
    <td>Row</td>
</tr>
<tr>
    <td></td>
    <td>Row</td>
</tr>
<tr>
    <td></td>
    <td>Row</td>
</tr>
<tr>
    <td></td>
    <td>Row</td>
</tr>
</table>

<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script>
$('table tr').each(function(i) {
    var number = i + 1;
    $(this).find('td:first').text(number);
});
</script>