KöMaL 2021 C1661
In a lottery game, the player bets 5 numbers out of the positive integers 1 to 90. Otto Lotter insists on increase, and he always keeps the following rules when making his bets: he marks 5 numbers such that every digit may only occur once, and if the five numbers are listed in increasing order, the digits must be ascending, too. For example, 1, 2, 3, 46, 78. How many suitable selections of five numbers are there?
Official text KöMaL. Quoted with source.
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