for integer "b" ≥ 2, a thabit number base "b is a number of the form ("b"+1)·"b" − 1 for a non-negative integer "n". also, for integer "b" ≥ 2, a thabit number of the second kind base "b is a number of the form ("b"+1)·"b" + 1 for a non-negative integer "n".