I think you're looking for a factorial number system [1] and/or Lehmer code [2]. [1] https://en.wikipedia.org/wiki/Factorial_number_system https://en.wikipedia

I think you're looking for a factorial number system [1] and/or Lehmer code [2]. [1] https://en.wikipedia.org/wiki/Factorial_number_system https://en.wikipedia.org/wiki/Factorial_number_system [2] https://en.wikipedia.org/wiki/Lehmer_code https://en.wikipedia.org/wiki/Lehmer_code