[bes]

<style>
	table, td {
		border: solid 1px;
		text-align: center;
		white-space: nowrap;
	}
</style>

<input id="inp">
<div id="div"></div>

<script>
window.onload = function () {
	var num = 20;
	
	var str = '<table id="table"><tr><td>a x b, mm</td>';

	for (var i = 1; i <= num; i++) {
		str += '<td>' + i*50 + '</td>';
	}
	str += '</tr>';


	for (i = 1; i <= num; i++) {
		str += '<tr>';
		for (var j = 0; j <= num; j++) {
			if (j == 0) {
				str += '<td>' + i*50 + '</td>';
			} else {
				str += '<td>' + i * 50 * j * 50 + '</td>';
			}
		}
		str += '</tr>' 
	}
	str += '</table>';
	
	document.getElementById('div').innerHTML = str;


	var table = document.getElementById('table');
	var inp = document.getElementById('inp');
	var tr = table.rows;
	var len = tr.length;
	var td, tdLen;
	var value;

	function calculate() {
		if (isNaN(inp.value) == false && inp.value != '') {
			value = parseFloat(inp.value);
		} else {
			value = 1;
		}
		for (var i = 1; i < len; i++) {
			td = tr[i].cells;
			tdLen = td.length;
			for (var j = 1; j < tdLen; j++) {
				td[j].innerHTML = i * 50 * j * 50 * value;
			}
		}
	}


	 inp.onkeyup = function () {
		calculate()
	}

}
</script>