|
%I #33 Feb 18 2021 12:35:55
%S 0,1,2,3,5,7,9,14,23,129,198,235,275,630,870,1033,1290,3293,3458,
%T 11466,13885,25893,32186,33139,58125,78929,97197,121933,128422,442674
%N Numbers n such that 7^n + 4 is prime.
%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
%E a(28)-a(29) from Lelio R. Paula, Nov 2014
%E a(30) from _Paul Bourdelais_, Feb 11 2021
|
