http://blog.greweb.fr/?p=2011

missing_numbers.js

var n = 1000;
var from = 10000000000000000;
var to = from + n;
var i = from;
var missing = [];
while (i < to) {
  var incr = 1;
  while (i === i+incr) {
    missing.push(i+" + "+incr);
    incr ++;
  }
  i += incr;
}
console.log(missing);
console.log(missing.length+" values are missing."); 
// logs: 250 values are missing.