Ionacarr, odd digits are 1,3,5,7,9 (as normal) and B,D,F, which represent 11,13 and 15. So the only choices for each of the thee cells in 5dn are B, D or F, with two of those repeated.
Similarly, if any of the odd numbers (the last property) end in a letter they must end in B, D or F.
You cannot assume that such numbers contain only decimal odd numbers before conversion. For instance FFD contains all odd hex digits, but FFD is decimal 4093, which has only two odd digits.