I can't work out whether you have 3, 4 or 5 clues? Is 2,4,8 a letter count or a question?
Are we looking for people, TV programmes, capital cities or what?
2, 4, 8 could be Dublin (doubling)
noddy2, what they are saying is that we are no looking for a capital with the letters 2,4,8, double2 is 4 double 4 is 8 etc. so you are doubling numbers - so answer is Dublin