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A096305 Numbers n such that 7^n + 4 is prime. 11

%I

%S 0,1,2,3,5,7,9,14,23,129,198,235,275,630,870,1033,1290,3293,3458,

%T 11466,13885,25893,32186,33139,58125,78929,97197

%N Numbers n such that 7^n + 4 is prime.

%C a(28) > 10^5. - _Robert Price_, Jan 24 2014

%e 7^14 + 4 = 678223072853 is a prime number.

%t Do[If[PrimeQ[7^n+4], Print[n]], {n, 1, 1000}]

%o (PARI) for(n=0, 10^5, if(ispseudoprime(7^n+4), print1(n, ", "))) \\ _Felix Fröhlich_, Jun 04 2014

%Y Cf. A236371, A217131, A191469, A090669, A096305, A217130, A217132, A152213.

%K nonn,more

%O 1,3

%A Herman H. Rosenfeld (herm3(AT)pacbell.net), Jun 26 2004

%E More terms (probable primes) from _Rick L. Shepherd_, Jun 29 2004

%E 7 more terms from _Jason Earls_, Feb 16 2008

%E a(25)-a(27) from _Robert Price_, Jan 24 2014

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Last modified July 15 03:05 EDT 2020. Contains 335762 sequences. (Running on oeis4.)