%I

%S 1,3,9,15,180,747,1065

%N Numbers n such that 10^n-2^n-1 is prime.

%C a(8) > 50000. - _Jens Kruse Andersen_, Aug 10 2014

%o (MAGMA) [n: n in [1..700] | IsPrime(10^n-2^n-1) ]

%o (PARI) is(n)=ispseudoprime(10^n-2^n-1) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A173852.

%K nonn,hard,more

%O 1,2

%A _Vincenzo Librandi_, Mar 11 2010

%E a(6)-a(7) from _Jens Kruse Andersen_, Aug 10 2014