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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

Contribution from Enrique Pérez Herrero, Jul 29 2010: (Start)

With: f(n)=3^(2n-1)+2, the non primality for f(n) is settled when:

if 2 does not divides 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.

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: A026369 A269818 A006552 * A212892 A227971 A267661

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 November 20 10:41 EST 2017. Contains 294963 sequences.