%I #14 Jul 14 2019 08:32:55

%S 5,7,11,29,79,83,241,727,6563,19681,59051,4782971,14348909,

%T 31381059607,282429536483,2541865828331,150094635296999123,

%U 450283905890997361,36472996377170786401,1144561273430837494885949696429

%N Prime numbers of the form 3^k +- 2 for k >= 1.

%C a(49) = 3^2224 - 2 and a(50) = 3^2521 - 2 are too big for a b-file. - _Robert Israel_, Nov 22 2015

%H Robert Israel, <a href="/A144231/b144231.txt">Table of n, a(n) for n = 1..48</a>

%p A:= NULL:

%p for k from 1 to 1000 do

%p t:= 3^k;

%p if isprime(t-2) then A:= A, t-2 fi;

%p if isprime(t+2) then A:= A, t+2 fi;

%p od:

%p A; # _Robert Israel_, Nov 22 2015

%t Reap[For[k = 1, k <= 100, k++, p = 3^k-2; If[PrimeQ[p], Sow[p]]; If[PrimeQ[p+4], Sow[p+4]]]][[2, 1]] (* _Jean-François Alcover_, Dec 18 2013 *)

%Y Cf. A000040, A000668, A014232, A057735.

%K nonn

%O 1,1

%A _Reikku Kulon_, Sep 15 2008