October 2018 Fiendish Function

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

  • GUESS
  • REPLY
  • 1
  • 2
  • 2
  • 3
  • 3
  • 6
  • 4
  • 13
  • 5
  • 28
  • 10
  • 1015

The rule was: "The number subtracted from two to the power of the number, then add one".

Suppose the guess was 13:

  • Calculate two to the power of the number, giving 8192.
  • Subtract the number from this, giving 8179.
  • Add one, giving 8180.

So the result is 8180.