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# Problem 303

Multiples with small digits

For a positive integer n, define f(n) as the least positive multiple of n that, written in base 10, uses only digits ≤ 2.

Thus f(2)=2, f(3)=12, f(7)=21, f(42)=210, f(89)=1121222.

Also, $\sum^{100}_{n=1}\frac{f(n)}{n}=11363107$.

Find $\sum^{10000}_{n=1}\frac{f(n)}{n}$.