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%I #23 Sep 08 2022 08:46:05
%S 0,1,2,5,7,8,20,25,43,95,326,383,434,517,884,1147,1303,2779,17237,
%T 49867,81427,100967
%N Numbers n such that 7*3^(2*n)+5*3^n+1 is prime.
%C a(23) > 150000. - _Robert Price_, Apr 05 2015
%H Eric L. F. Roettger, <a href="http://people.ucalgary.ca/~hwilliam/files/A_Cubic_Extention_of_the_Lucas_Functions.pdf">A Cubic Extension of the Lucas Functions</a>, Ph. D. Dissertation, Dept. Math. and Statistics, Univ. Calgary, 2009 (see page 196).
%t Select[Range[0, 3000], PrimeQ[7 3^(2 #) + 5 3^# + 1] &]
%o (Magma) [n: n in [0..1000] | IsPrime(7*3^(2*n)+5*3^n+1)]; // _Vincenzo Librandi_, Apr 06 2015
%o (PARI) is(n)=ispseudoprime(7*3^(2*n)+5*3^n+1) \\ _Charles R Greathouse IV_, Jun 13 2017
%Y Cf. A058603.
%K nonn,more
%O 1,3
%A _Vincenzo Librandi_, Jul 14 2013
%E a(19)-a(22) from _Robert Price_, Apr 05 2015