# self-descriptive number

## Primary tabs

Synonym:
self descriptive number
Type of Math Object:
Definition
Major Section:
Reference

## Mathematics Subject Classification

### how to describe algebraically

I'm not entirely sure d_x = \sum_{d_i = x} is correct. I understand what it means (digit y at position x is the total number of instances of digit y in the number) but I'm not sure if the formula is mathematically correct. Can this be fed to a CAS so that it understands what is meant?