var popular=document.getElementById('aSpecificNumberOfGreyShades'), html='', apparentlyMagicNumber=50; for (var shade=1; shade<=apparentlyMagicNumber; shade++){ var grey = parseInt((200/60)*shade + 30); html+='<div style="background-color:rgb('+ grey+','+grey+','+grey+ ')"> '+(shade<10?'0'+shade:shade)+' </div>'+ ((1+shade)%10==1?"<br>":""); } popular.innerHTML=html;