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A374151
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The number of prime-indexed primes below 2^n.
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2
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0, 0, 1, 2, 3, 5, 7, 11, 16, 25, 39, 63, 103, 172, 290, 490, 844, 1464, 2564, 4522, 8022, 14325, 25686, 46382, 84115, 153327, 280423, 514798, 948374, 1752639, 3248574, 6037968, 11250482, 21013808, 39336188, 73788697, 138689231, 261150360, 492602752, 930716294
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OFFSET
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0,4
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COMMENTS
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The data was calculated using Kim Walisch's primecount program.
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LINKS
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FORMULA
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EXAMPLE
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a(1) = 0 since primepi(primepi(2^1)) = primepi(primepi(2)) = primepi(1) = 0.
a(2) = 1 since primepi(primepi(2^2)) = primepi(primepi(4)) = primepi(2) = 1.
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MATHEMATICA
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Table[PrimePi[PrimePi[2^n]], {n, 0, 40}]
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PROG
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(PARI) a(n) = primepi(primepi(2^n));
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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