A number is called 8-substring-friendly if every one of its digits belongs to a 8-substring. For example, 352114 is 8-substring-friendly, but 26(5)44 is not. For a given n, find T(n) the number of ...

Substring returns characters from a string, starting from the specified position, or index. Index values start with the number 0. Examples: substring('This_is_a ...