%I #8 Jun 08 2021 18:01:29
%S 11,211,511111,71111111,101111111111,161111111111111111,
%T 2011111111111111111111,
%U 6511111111111111111111111111111111111111111111111111111111111111111
%N Primes of the form n (written in base 10) followed by n 1's.
%t Do[p = FromDigits[ Join[ IntegerDigits[n], IntegerDigits[(10^n - 1)/9]]]; If[ PrimeQ[p], Print[p]], {n, 1, 100}]
%t Select[Table[FromDigits[Join[IntegerDigits[n],PadRight[{},n,1]]],{n,100}],PrimeQ] (* _Harvey P. Dale_, Jun 08 2021 *)
%Y Cf. A068817 (for values of n).
%K base,nonn
%O 1,1
%A _Amarnath Murthy_, May 02 2002
%E More terms from _Vladeta Jovovic_ and _Robert G. Wilson v_, May 03 2002