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Numbers k such that 3^k + 8 is prime.
18

%I #11 Nov 09 2023 11:37:12

%S 1,2,4,5,8,13,14,20,38,44,77,88,124,152,244,557,2429,4382,6268,18488,

%T 75097,81998,96460,143497

%N Numbers k such that 3^k + 8 is prime.

%C a(25) > 2*10^5. - _Robert Price_, Sep 25 2013

%t Select[Range[0, 5000], PrimeQ[3^# + 8] &]

%o (PARI) for(n=1, 5*10^3, if(isprime(3^n+8), print1(n", ")))

%Y Cf. A014224, A051783, A058958, A058959.

%K nonn

%O 1,2

%A _Vincenzo Librandi_, Oct 01 2012

%E a(19)-a(24) from _Robert Price_, Sep 25 2013