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A196446
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Numbers n such that both n and (n-1)^2*2^n-1 are primes.
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1
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2, 3, 19, 29, 43, 61, 79, 109, 151, 167, 2311
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OFFSET
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1,1
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COMMENTS
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Primes p such that (p-1)^2*2^p-1 is also prime.
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LINKS
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EXAMPLE
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a(1)=2 because 2 is a prime and (2-1)^2*2^2-1=3 is a prime,
a(2)=3 because 3 is a prime and (3-1)^2*2^3-1=31 is a prime,
a(3)=19 because 19 is a prime and (19-1)^2*2^19-1=169869313 is a prime,
a(4)=29 because 29 is a prime and (29-1)^2*2^29-1=420906795007 is a prime.
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MATHEMATICA
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Select[Prime[Range[40]], PrimeQ[(#-1)^2 2^#-1]&] (* The program generates the first 10 terms *) (* Harvey P. Dale, Sep 06 2017 *)
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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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