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 A134753 Numbers n such that 3^(2*n-1) + 2 is prime. 2
 1, 2, 8, 32, 62, 70, 118, 122, 158, 182, 196, 566, 752, 3602, 21896, 22768, 53072 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS From Enrique Pérez Herrero, Jul 29 2010: (Start) With: f(n)=3^(2n-1)+2, the non-primality of f(n) is settled when: if 2 does not divide n, 5 divides f(n) (n>1) if 3 divides n, 7 divides f(n) if 5 divides n-4, 11 divides f(n) if 14 divides n-2, 29 divides f(n) if 15 divides n-5, 31 divides f(n). (End) REFERENCES Luis H. Gallardo, Posting to the Number Theory List, Jan 14 2008 LINKS Table of n, a(n) for n=1..17. L. H. Gallardo, On a remark of Makowski about perfect numbers, El. Mathem. 65 (3) (2010) 121-126 Henri & Renaud Lifchitz, PRP Records. FORMULA ({odd terms in A051783} + 1)/2. MATHEMATICA Contribution from Enrique Pérez Herrero, Jul 29 2010: (Start) MaxVal = 1000; dataA134753=Select[Select[Range[MaxVal], #<3||Mod[#, 2]==0&&Mod[#, 3]!=0&&Mod[#, 5]!=4&&Mod[#, 14]!=2&&Mod[#, 15]!=5&], PrimeQ[3^(2*#-1)+2]&] A134753[n_Integer] := dataA134753[[n]] /; (n > 0 && n <= Length[dataA134753]) (End) PROG (PARI) is(n)=isprime(3^(2*n-1)+2) \\ Charles R Greathouse IV, Jun 06 2017 CROSSREFS Cf. A051783, A134752. Sequence in context: A269818 A331823 A006552 * A212892 A302936 A227971 Adjacent sequences: A134750 A134751 A134752 * A134754 A134755 A134756 KEYWORD nonn,easy AUTHOR N. J. A. Sloane, Jan 28 2008 EXTENSIONS Typo in prime search corrected Enrique Pérez Herrero, Jul 31 2010 a(15)-a(17) from A051783 by Ray Chandler, Aug 06 2011 STATUS approved

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Last modified August 3 18:16 EDT 2024. Contains 374899 sequences. (Running on oeis4.)