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A172461
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Primes p such that 2*p-1 and 2^p-1 are both primes.
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3
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2, 3, 7, 19, 31, 607, 1279, 2281, 44497, 1257787, 13466917
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OFFSET
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1,1
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LINKS
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EXAMPLE
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a(1) = 2 is a term since it is a prime and 2^2 - 1 = 3 and 2*2 - 1 = 3 are primes.
a(2) = 3 is a term since it is a prime and 2^3 - 1 = 7 and 2*3 - 1 = 5 are primes.
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MATHEMATICA
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Select[MersennePrimeExponent[Range[47]], PrimeQ[2# -1] &] (* Amiram Eldar, Jul 29 2020 *)
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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