Isn't this what classes are for? Add a class, let's call it myButton
to all your buttons and then use that as a selector.
$("#content").on('click','.myButton', function(){
Alternatively, if you insist on using ids, this ought to work:
var buttons = '#buttonID1, #buttonID2, #buttonID3, #buttonID4';
$("#content").on('click',buttons, function(){