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Numbers n such that 7^n + 6^(n + 1) is prime.
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%I #13 Sep 08 2022 08:46:15

%S 0,1,4,5,12,16,27,87,252,1052,1691,3237,3669,16140,17072,27932,70811

%N Numbers n such that 7^n + 6^(n + 1) is prime.

%C a(18) > 10^5.

%t Select[Range[0,100000], PrimeQ[7^# + 6^(# + 1)] &]

%o (Magma) [n: n in [0..500] | IsPrime(7^n+6^(n+1))]; // _Vincenzo Librandi_, Jul 12 2016

%o (PARI) is(n)=ispseudoprime(7^n+6^(n+1)) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A093765.

%K nonn,more

%O 1,3

%A _Robert Price_, Jul 11 2016