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OFFSET
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1,1
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COMMENTS
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First four terms are primes. Fifth (1.61585...*10^616), sixth (5.45374...*10^2465), seventh (2.007...*10^39456) and eighth (1.298...*10^157826) are not primes.
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LINKS
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Table of n, a(n) for n=1..4.
Eric Weisstein's World of Mathematics, Double Mersenne Number
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FORMULA
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a(n) =A077585(A000040(n)) =A000225(A001348(n))
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EXAMPLE
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a(3)=2^(2^5-1)-1=2^31-1=2147483647.
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MATHEMATICA
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lst={}; Do[p=Prime[n]; If[PrimeQ[x=2^(2^p-1)-1], Print[x]; AppendTo[lst, n]], {n, 10^9}]; lst [From Vladimir Joseph Stephan Orlovsky, Aug 21 2008]
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CROSSREFS
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Sequence in context: A077585 A134722 A053713 * A002614 A187237 A095885
Adjacent sequences: A077583 A077584 A077585 * A077587 A077588 A077589
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KEYWORD
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nonn
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AUTHOR
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Henry Bottomley, Nov 07 2002
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STATUS
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approved
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