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Numbers k such that 3*7^k - 2 is prime.
1

%I #15 Jul 09 2024 08:53:28

%S 1,11,168,185,467,767,1400,1428,1736,2516,3275,3540,51156

%N Numbers k such that 3*7^k - 2 is prime.

%C a(13) > 37584. - _Jinyuan Wang_, Jan 21 2020

%t Do[ If[ PrimeQ[ 3*7^n - 2 ], Print[n] ], {n, 1, 5000} ]

%o (PARI) is(n)=ispseudoprime(3*7^n-2) \\ _Charles R Greathouse IV_, Jun 13 2017

%o (Magma) [k: k in [0..1000] | IsPrime(3*7^k-2)]; // _Jinyuan Wang_, Jan 21 2020

%Y Cf. A059041 (3*7^k+2 is prime).

%K nonn,more

%O 1,2

%A _Robert G. Wilson v_, Feb 12 2001

%E a(13) from _Michael S. Branicky_, Jul 09 2024