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A273814 Numbers n such that (12^n - 7^n)/5 is prime. 1

%I

%S 2,3,7,13,47,89,139,523,1051

%N Numbers n such that (12^n - 7^n)/5 is prime.

%C All terms are prime.

%C The corresponding primes are 19, 277, 7001653, 21379263273733, 105329145253605843602014309589572596276217801876213, ...

%p A273814:=n->`if`(isprime((12^n - 7^n)/5), n, NULL): seq(A273814(n), n=1..10^3); # _Wesley Ivan Hurt_, Jun 01 2016

%t Select[Range[1, 10000], PrimeQ[(12^# - 7^#)/5] &]

%o (PARI) for(n=1, 10000, if(isprime((12^n - 7^n)/5), print1(n, ", ")))

%Y Cf. A004064, A062578, A128348.

%K nonn,more,hard

%O 1,1

%A _Tim Johannes Ohrtmann_, May 31 2016

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Last modified June 19 17:16 EDT 2019. Contains 324222 sequences. (Running on oeis4.)