<script>
<!-- Конкретный рандом
var r_text = new Array ();
r_text[0] = "1";
r_text[1] = "2";
r_text[2] = "3";
r_text[3] = "4";
r_text[4] = "5";
r_text[5] = "6";
r_text[6] = "7";
r_text[7] = "8";
r_text[8] = "9";
r_text[9] = "10";
r_text[10] = "11";
r_text[11] = "12";
r_text[12] = "13";
r_text[13] = "14";
r_text[14] = "15";
r_text[15] = "16";
r_text[16] = "17";
r_text[17] = "18";
r_text[18] = "19";
r_text[19] = "20";
r_text[20] = "21";
r_text[21] = "22";
r_text[22] = "23";
r_text[23] = "24";
r_text[24] = "25";
r_text[25] = "26";
r_text[26] = "27";
r_text[27] = "28";
r_text[28] = "29";
r_text[29] = "30";
for (i=0;i<19;i++)
{
var s = Math.floor(30*Math.random())
document.write(r_text[s]);
document.write("<br />");
}
//-->
</script>

<script language='JavaScript'>
var r_text = new Array(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30);

var cnt=0;
var printed=new Array();

while(true)
{
  var s=Math.floor(30*Math.random());

  if(!printed[s])
  {
    document.write(r_text[s]+"<br>");
    printed[s]=1;
    cnt++;
  }

  if(cnt==19)
    break;
}
</script>

document.write
(
  (function(a, i, l)
  {
    while((a[i] = ++i) < l);
    return a;
  })
  ([], 0, 30).sort(function()
  {
    return Math.random() > 0.5;
  })
  .slice(0, 19)
);