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There are only 8 positive integers n for which the number of primes < n (pi(n)) equals the number of positive integers < n relative prime to n (phi(n)). They are 2, 3, 4, 8, 10, 14, 20, and 90. [Moser] (90^{3}  1)/(90  1) is a Mersenne prime. [Goormaghtigh]
(There are 4 curios for this number that have not yet been approved by an editor.)
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