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Problem 864

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Square + 1 = Squarefree

Let $C(n)$ be the number of squarefree integers of the form $x^2+1$ such that $1\le x\le n$.

For example, $C(10)=9$ and $C(1000)=895$.

Find $C(123567101113)$.

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平方数 + 1 = 无平方因子数

记$C(n)$为所有形如$x^2+1$的无平方因子数的数目，其中$1\le x\le n$。

例如，$C(10)=9$，$C(1000)=895$。

求$C(123567101113)$。

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