Squarefree Numbers

A positive integer $n$ is called squarefree, if no square of a prime divides $n$ , thus $1, 2, 3, 5, 6, 7, 10, 11$ are squarefree, but not $4, 8, 9, 12$ .

How many squarefree numbers are there below $2^{50}$ ?

Write-up coming later

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