This reminds me of "zeroless number systems" or "bijective number systems" (https://en.wikipedia.org/wiki/Bijective_numeration#The_bijective_base-10_system http

This reminds me of "zeroless number systems" or "bijective number systems" (https://en.wikipedia.org/wiki/Bijective_numeration#The_bijective_base-10_system https://en.wikipedia.org/wiki/Bijective_numeration#The_bijec...) - in the language of the article, the allowed digits in base 10 are 123456789A. Note that 0 is not an allowed digit. For instance here are the first few natural numbers in this system: 1,2,3,4,5,6,7,8,9,A,11,12... I first read about them in Chris Okasaki's purely functional data structures book, they have some applications in terms of designing data structures (e.g. combining perfect-powers-of-two sized heaps to build heaps of arbitrary size). They're conceptually interesting too, being a positional number system with no redundancy (exactly one way to represent each number) and without 0. Since the concept of a 0 digit is not required, one could argue that it's conceptually easier for e.g. a classical Roman mathematician to learn this than the positional system we do use today. Also, excel's system for numbering columns uses this - A, B, C, ... X, Y, Z, AA, AB ...