

A089213


Primes p such that either 3^p2 or 3^p+2 is prime.


0




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



