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Numbers k such that 5^(k+3) + 3^(k+2) + 2^(k+1) + 1 is prime.
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%I #25 Nov 11 2024 14:14:13

%S 0,4,8,524,972,3780,7704

%N Numbers k such that 5^(k+3) + 3^(k+2) + 2^(k+1) + 1 is prime.

%C Larger k values yield probable primes.

%C a(8) > 100000 (if it exists). - _Michael S. Branicky_, Nov 11 2024

%t ParallelTable[If[PrimeQ[5^(n+3) + 3^(n+2) + 2^(n+1) + 1], n, Nothing], {n, 0, 10^4}]

%Y Cf. A306573.

%K nonn,hard,more

%O 1,2

%A _Mikk Heidemaa_, Jun 07 2019