March 2018 Fiendish Function

The Fiendish Function posed during March 2018 had the following sample guesses and replies:

  • GUESS
  • REPLY
  • 1
  • 2
  • 2
  • 2
  • 3
  • 4
  • 4
  • 2
  • 5
  • 6
  • 10
  • 6

The rule was: "Write the number in binary, reverse it, and then convert it back to decimal, then add one".

Suppose the guess was 39:

  • Write this in binary, giving 100111.
  • Reverse it, giving 111001
  • Convert this back to decimal, giving 57.
  • Add one, giving 58.

So the result is 58.