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Numbers n such that 5^n-4^(n-1) is prime.
0

%I #22 Jun 13 2017 14:33:33

%S 3,11,25,341,1827,2581,4475,11157,41141,64721

%N Numbers n such that 5^n-4^(n-1) is prime.

%C a(11) > 10^5.

%e 3 is a member since 5^3 - 4^2 = 125 - 16 = 109 which is a prime number.

%t Select[Range[0, 100000], PrimeQ[5^# - 4^(# - 1)] &]

%o (PARI) is(n)=ispseudoprime(5^n-4^(n-1)) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A093713, A082103, A093717, A093793, A096185, A093794, A093795, A096186, A271883, A271884, A272345.

%K nonn,more

%O 1,1

%A _Robert Price_, Apr 27 2016