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A089213 Primes p such that either 3^p-2 or 3^p+2 is prime. 0
2, 3, 5, 37, 41, 139, 317, 541, 2521 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

At p = 2, 3, 139, 3^p + 2 is prime, while at p = 2, 5, 37, 41, 317, 541, 2521 3^p - 2 is prime.

a(10) > 2*10^5. - Robert Price, Nov 20 2013

LINKS

Table of n, a(n) for n=1..9.

EXAMPLE

2 is in the sequence because both 3^2 - 2 = 7 and 3^2 + 2 = 11 are primes.

3 is in the sequence because 3^3 + 2 = 29 is a prime (though 3^3 - 2 = 25 = 5^2).

5 is in the sequence because 3^5 - 2 = 241 is a prime (though 3^5 + 2 = 245 = 5 * 7^2.

MATHEMATICA

Select[Prime[Range[100]], PrimeQ[3^# - 2] || PrimeQ[3^# + 2] &] (* Alonso del Arte, Nov 20 2013 *)

CROSSREFS

Cf. A014224, A051783.

Sequence in context: A041977 A261130 A271387 * A029499 A128026 A041443

Adjacent sequences:  A089210 A089211 A089212 * A089214 A089215 A089216

KEYWORD

nonn

AUTHOR

Herman H. Rosenfeld (herm3(AT)pacbell.net), Dec 20 2003

EXTENSIONS

Edited by Zak Seidov, Aug 08 2006

STATUS

approved

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Last modified July 23 12:35 EDT 2019. Contains 325254 sequences. (Running on oeis4.)