True or false? (I don't know.) Every positive integer is the difference of two powers. Examples: $ 1 = 3^2 - 2^3 $
$ 2 = 3^3 - 5^2 $
$ 3 = 2^7-5^3 $
$ 4 = 2^3-2^2 = 5^3-11^2 $
$ 5 = 2^5 - 3^3 $
$ 6 = ? $
$ 7 = 2^5-5^2 $
$ 8 =? $
$ 9 = 5^2-2^4 $