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A066719
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Numbers n such that 1+n^phi(n) is prime.
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2
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OFFSET
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1,2
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LINKS
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EXAMPLE
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4^phi(4) + 1 = 4^2 + 1 = 17, a prime, so 4 is a term of the sequence.
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MATHEMATICA
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Do[s=1+n^(EulerPhi[n]); If[PrimeQ[s], Print[{n, s}]], {n, 1, 1000}]
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PROG
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(PARI) for(n=1, 6000, print(n); s=1+n^eulerphi(n); if(isprime(s), print(n, " ", s)))
/* It suffices to search only even n - with, e.g., PARI forstep (n=6002, 7000, 2, ...) - because a(1)=1 is the only possible odd term. (Note that the average number of digits of s ( length(Str(s)) ) for the 500 even candidates from 6002 to 7000 is 10048 with a minimum of 5087 digits and a maximum of 13450 digits). */
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CROSSREFS
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KEYWORD
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nonn,hard
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AUTHOR
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EXTENSIONS
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Further terms are greater than 10,000.
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STATUS
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approved
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