Let n be a positive integer such that 2n-1 is a digit anagram of n (in its decimal representation). An example of such a pair would be n=37, 2n-1=73.
Show that if n's least significant digit is 3, n must also contain an 8.
(In reply to some examples--for what they're worth
Why digit 2 never appears in n and 2n-1 ?