July 2018 Fiendish Function

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

  • GUESS
  • REPLY
  • 1
  • 1
  • 2
  • 5
  • 3
  • 10
  • 4
  • 21
  • 5
  • 26
  • 10
  • 130

The rule was: "Add the squares of the number's divisors together".

Suppose the guess was 15:

  • Find the number's divisors, giving 1, 3, 5, 15
  • Square them, giving 1, 9, 25, 225
  • Add these together, giving 260.

So the result is 260.