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A125738
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Primes p such that 3^p - 3^((p + 1)/2) + 1 is prime.
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3
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OFFSET
| 1,1
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COMMENTS
| PrimePi[ a(n) ] = {2, 5, 44, 52, 120, 127, 185,...}.
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LINKS
| J. Brillhart et al., Factorizations of b^n +- 1, Contemporary Mathematics, Vol. 22, Amer. Math. Soc., Providence, RI, 3rd edition, 2002.
S. S. Wagstaff, Jr., The Cunningham Project.
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MATHEMATICA
| Do[p=Prime[n]; f=3^p-3^((p+1)/2)+1; If[PrimeQ[f], Print[{n, p}]], {n, 1, 200}]
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CROSSREFS
| Cf. A125739 = Primes p such that 3^p + 3^((p + 1)/2) + 1 is prime. Cf. A007670 = numbers n such that 2^n - 2^((n + 1)/2) + 1 is prime. Cf. A007671 = numbers n such that 2^n + 2^((n + 1)/2) + 1 is prime.
Sequence in context: A118479 A103836 A081484 * A092840 A007156 A060346
Adjacent sequences: A125735 A125736 A125737 * A125739 A125740 A125741
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KEYWORD
| hard,more,nonn
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AUTHOR
| Alexander Adamchuk (alex(AT)kolmogorov.com), Dec 02 2006
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