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Prime numbers of the form 10^k +- 9.
2

%I #4 Jul 22 2016 10:57:11

%S 19,109,991,1009,10009,99991,9999991,1000000009,1000000000000000009,

%T 10000000000000000000009,999999999999999999999999999999991,

%U 999999999999999999999999999999999999999999991

%N Prime numbers of the form 10^k +- 9.

%C This sequence illustrates the base-n representation of numbers having the form n^k +- (n - 1).

%t Select[Sort[Flatten[Table[10^n+{9,-9},{n,50}]]],PrimeQ] (* _Harvey P. Dale_, Jul 22 2016 *)

%Y Cf. A000040, A000668, A144231, A144232, A144233, A144234, A144236, A144242, A144245

%K nonn

%O 1,1

%A _Reikku Kulon_, Sep 15 2008