%I #39 Apr 06 2018 07:48:25
%S 0,1,3,15,45,117,159,3739,3777,9703,10623,21459,86595
%N Numbers k such that 3^k + k + 1 is a prime.
%p a:=n->`if`(isprime(3^k+k+1),k,NULL): seq(a(k),k=0..6000); # _Muniru A Asiru_, Mar 25 2018
%t Flatten[{0, Select[Range[5000], PrimeQ[3^# + # + 1] &]}] (* _Vaclav Kotesovec_, Mar 25 2018 *)
%o (PARI) for(n=0, 1000, if(isprime(3^n+n+1), print1(n", ")))
%Y A182327 gives the primes.
%Y Cf. A171058, A173053, A301633.
%K nonn,more,hard
%O 1,3
%A _Seiichi Manyama_, Mar 25 2018
%E a(8)-a(9) from _Muniru A Asiru_, Mar 25 2018
%E a(10)-a(11) from _Vaclav Kotesovec_, Mar 25 2018
%E a(12) from _Altug Alkan_, Apr 01 2018
%E a(13) from _Giovanni Resta_, Apr 06 2018