[seqfan] What is the name for a string that contains every k-digit base-b substring?

[Marc LeBrun]

What is the name for a string that contains every k-digit base-b substring?

For example, with k=3 and b=10 this would be a string that contains every
three-digit decimal number as a substring.

I'm interested in OEIS sequences related to this property (eg shortest,
number-of, etc) but need some idea what they are called to search on it!

Thanks!
  --MLB