login
Numbers k such that 3^k + k + 1 is a prime.
3

%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