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Integers up to ten thousand containing a zero

Question

Among the integers 1,2,…,100001,2,\dots,10000, how many contain at least one digit 00?

Short answer

26202620. Count the zero-free ones instead: 9+92+93+94=73809+9^2+9^3+9^4=7380 numbers with one to four digits, and 1000010000 itself contains zeros. So 10000−7380=262010000-7380=2620.

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