1, 3, 5, 7, 9, 15, 17, 21, 27, __, __, __, ...

What are the next three numbers in this sequence?

Each term of the given sequence is the decimal representation of palindromic binary numbers.

Now 27 = 11011 in binary.

The next three palindromic numbers are:

11111, 100001, 101101 and these are respectively 31, 33 and 45 in decimal representation.

Thus, the required missing numbers are: 31, 33 and 45.