%I #7 Jun 13 2017 10:16:57

%S 2,260,650,1928,5768

%N Numbers k such that (9*10^k-11)/7 is prime.

%C All terms are of the form 2+6*k, k=0,1,... Next term > 7220. Are there any n's such that (9*10^n-11)/p is prime for prime p<>7? Cf. A100275 = Numbers n such that 9*10^n-11 is prime.

%t Do[If[PrimeQ[(9*10^n-11)/7],Print[n]],{n,2,7220,6}]

%o (PARI) is(n)=ispseudoprime((9*10^n-11)/7) \\ _Charles R Greathouse IV_, Jun 13 2017

%Y Cf. A100275.

%K nonn

%O 1,1

%A _Zak Seidov_, Sep 22 2006