Let be the set of all positive integers between 1 and 2017, inclusive. Suppose that the least common multiple of all elements in is . Find the number of elements in that do not divide .
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We have L = 2 1 0 ⋅ 3 6 ⋅ 7 3 ⋅ P , where P is a product of other prime powers. Then L / 2 0 1 6 = 2 5 ⋅ 3 4 ⋅ 7 2 ⋅ P . So we are looking for numbers which are divisible by 2 6 , or 3 5 , or 7 3 . No number ≤ 2 0 1 7 is divisible by two of these simultaneously, so we can count each one separately.
There are ⌊ 2 0 1 7 / 2 6 ⌋ = 3 1 numbers divisible by 2 6 , ⌊ 2 0 1 7 / 3 5 ⌋ = 8 numbers divisible by 3 5 , and ⌊ 2 0 1 7 / 7 3 ⌋ = 5 numbers divisible by 7 3 , so the answer is 3 1 + 8 + 5 = 4 4 .