I know four fours have been done here (not sure about 5 5s though)
You have to form the numbers from 0-whatever (in ascending order) using simple arithmetic operations. These being:
concatenation (eg: 55 or.55 etc...)
decimals . (ie .5)
recurring decimals (no overbar (or underline) so will let .5 denote .555555.... = 5/9)
square roots sqrt() (debatable because of implied 1/2 but then factorial has implied 2,3,4 in it yet no-one says anything about that)
Also since the first 30 or so are trivial should we start a bit later?