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 A128068 Numbers k such that (3^k + 8^k)/11 is prime. 8

%I

%S 5,163,191,229,271,733,21059,25237

%N Numbers k such that (3^k + 8^k)/11 is prime.

%C All terms are primes.

%C a(9) > 10^5. - _Robert Price_, Mar 06 2013

%t k=8; Do[ p=Prime[n]; f=(3^p+k^p)/(k+3); If[ PrimeQ[f], Print[p]], {n,1,100} ]

%o (PARI) is(n)=isprime((3^n+8^n)/11) \\ _Charles R Greathouse IV_, Feb 17 2017

%Y Cf. A007658 = numbers n such that (3^n + 1)/4 is prime. Cf. A057469 = numbers n such that (3^n + 2^n)/5 is prime. Cf. A122853 = numbers n such that (3^n + 5^n)/8 is prime. Cf. A128066, A128067, A128069, A128070, A128071, A128072, A128073, A128074, A128075. Cf. A059801 = numbers n such that 4^n - 3^n is prime. Cf. A121877 = numbers n such that (5^n - 3^n)/2 is a prime. Cf. A128024, A128025, A128026, A128027, A128028, A128029, A128030, A128031, A128032.

%K hard,more,nonn

%O 1,1

%A _Alexander Adamchuk_, Feb 14 2007

%E a(6) from _Alexander Adamchuk_, Feb 14 2007

%E a(7)-a(8) from _Robert Price_, Mar 06 2013

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Last modified June 26 10:12 EDT 2019. Contains 324375 sequences. (Running on oeis4.)