%I #35 Sep 08 2022 08:46:15
%S 1,2,3,14,19,21,27,33,46,70,80,441,540,567,625,1057,1119,1213,1542,
%T 4263,4419,4507,5186,7345,8626,8853,11256,12885,14688,15236,17697,
%U 26770,57801,71665
%N Numbers n such that 2*n*3^n + 1 is prime.
%C Primes: 2, 3, 19, 1213, 4507, ...
%C No further terms < 10^5. - _Ray Chandler_, Apr 13 2016
%e 1 is in this sequence because 2*1*3^1 + 1 = 7 is prime.
%t Select[Range[1600], PrimeQ[2 # 3^# + 1] &] (* _Vincenzo Librandi_, Jan 03 2016 *)
%o (Magma) [n: n in [1..2000]| IsPrime(2*n*3^n+1)]; // _Vincenzo Librandi_, Jan 03 2016
%o (PARI) is(n)=ispseudoprime(2*n*3^n+1) \\ _Charles R Greathouse IV_, Feb 08 2016
%Y Cf. A006552.
%K nonn,more
%O 1,2
%A _Juri-Stepan Gerasimov_, Jan 02 2016
%E a(24) and a(26) inserted by _Charles R Greathouse IV_, Feb 08 2016
%E a(28)-a(30) from _Charles R Greathouse IV_, Feb 08 2016
%E a(31)-a(32) from _Ray Chandler_, Apr 05 2016
%E a(33) from _Ray Chandler_, Apr 08 2016
%E a(34) from _Ray Chandler_, Apr 09 2016