Uniqueness means that if n is the sum of m distinct digits then there does not exist any other set of m distinct digits whose sum is n. This sequence may be useful for puzzle-digit games, often of oriental origin, like Kakuro, Kendoku, Sudoku-variants, etc.
16 belongs to this sequence because there exists only one set of two distinct digits whose sum is 16: {7, 9}. (Also, there exists only one set of five distinct digits whose sum is 16: {1, 2, 3, 4, 6}.) 6 belongs to this sequence because there exists only one set of three distinct digits whose sum is 6: {1, 2, 3}.
