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Numbers n such that 10^n + 9^(n+1) is prime.
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%I #7 Jun 13 2017 14:45:32

%S 2,3,6,11,44,64,83,123,166,381,446,1221,1540,3156,5117,5476,6291,6353,

%T 13053,15158,23904,78288,82254,91230

%N Numbers n such that 10^n + 9^(n+1) is prime.

%C a(25) > 10^5.

%e 3 is a member since 10^3 + 9^4 = 1000 + 6561 = 7561 which is a prime number.

%t Select[Range[0, 100000], PrimeQ[10^# + 9^(# + 1)] &]

%o (PARI) is(n)=ispseudoprime(10^n+9^(n+1)) \\ _Charles R Greathouse IV_, Jun 13 2017

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

%K nonn,more

%O 1,1

%A _Robert Price_, Aug 08 2016