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%I #16 Feb 17 2017 12:12:17
%S 1,3,37,119,255,355,371,497,1759,34863,50719,147709
%N Numbers n such that 10*11^n -1 is prime.
%C a(13) > 2*10^5. - _Robert Price_, Jan 19 2015
%D R. K. Guy, Unsolved Problems in Theory of Numbers, Section A3.
%H H. C. Williams, <a href="http://matwbn.icm.edu.pl/ksiazki/aa/aa39/aa3912.pdf">The primality of certain integers of the form 2Ar^n - 1</a>, Acta Arith. 39 (1981), 7-17.
%t Do[ If[ PrimeQ[10*11^n - 1], Print[n]], {n, 1, 2000}]
%o (PARI) is(n)=isprime(10*11^n-1) \\ _Charles R Greathouse IV_, Feb 17 2017
%Y Cf. A003307, A002235, A046865, A079906, A046866, A001771, A005541, A056725, A079907.
%K nonn,hard
%O 1,2
%A _N. J. A. Sloane_
%E One more term from _Robert G. Wilson v_, Jan 16 2003
%E a(10)-a(12) from _Robert Price_, Jan 19 2015
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