Repdigit (no ontology)
From Compile Worlds
A repdigit, also known as a monomial number, is a polynomial number of order 1, with all digits the same. As such, there are 9 repdigits for each digit-length of number; repdigits occupy 101-n of the population of n-digit numbers.
A repdigit with all digits 1 is also called a repunit.
Repdigits up to four digits long are listed as follows: