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A083351 Numbers n such that 5*7^n + 2 is prime. 0

%I

%S 0,1,4,9,12,25,132,192,459,10377,45130,63589,83265

%N Numbers n such that 5*7^n + 2 is prime.

%C Values corresponding to 9, 12, 25, 132, 192 and 459 (389 digits) have been certified prime with Primo. There are no other terms <= 4000.

%C No other terms <= 10^5. - _Tyler NeSmith_

%e 7, 37, 12007, 201768037, 69206436007, 6705343098319824504037

%e are 5*7^0 + 2, 5*7^1 + 2, 5*7^4 + 2, 5*7^9 + 2, 5*7^12 + 2, 5*7^25 + 2,

%e respectively. 5*7^132 + 2 has 113 digits.

%o (PARI) for(n=0,4000,if(isprime(5*7^n+2),print1(n,",")))

%K nonn

%O 1,3

%A _Rick L. Shepherd_, Apr 26 2003

%E a(10)-a(13) from _Tyler NeSmith_, Jan 17 2021

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Last modified December 2 14:09 EST 2021. Contains 349445 sequences. (Running on oeis4.)