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 57:

• Write this in binary, giving 111001.
• Reverse it, giving 100111
• Convert this back to decimal, giving 39.
• Add one, giving 40.

So the result is 40.