<html>
   <script>
      function getUrl() {
         var base = "https://projecteuler.net/problem=";
         var amount = 552; //Amount of problems at 21:00 31/05/2016
         var num = Math.random()*amount;
         var url = base + num; //Concetenate...

         document.getElementById("warning").innerHTML = "<br>Chances are, you have popups blocked and there is a notification in the top right.";
         return url;
      }
   </script>
   <button onclick="window.open(getUrl());">CLICK ME!</button>
   <a id="warning"></a>
</html>

Add File to open random problem
Add File to open random problem