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 A110680 Numbers n such that the string 4444n is prime. 2

%I

%S 9,21,43,49,61,63,69,73,87,109,127,147,159,169,171,201,207,213,217,

%T 229,241,261,289,291,331,339,357,369,381,397,409,469,471,483,487,507,

%U 519,549,591,607,621,639,663,669,697,703,711,717,729,747

%N Numbers n such that the string 4444n is prime.

%H Harvey P. Dale, <a href="/A110680/b110680.txt">Table of n, a(n) for n = 1..1000</a>

%e n=109 is in the sequence because 4444n = 4444109 is prime.

%t Select[Range[800],PrimeQ[4444*10^IntegerLength[#]+#]&] (* _Harvey P. Dale_, Jul 04 2014 *)

%K nonn,base

%O 1,1

%A _Parthasarathy Nambi_, Sep 14 2005

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Last modified December 15 15:10 EST 2019. Contains 329999 sequences. (Running on oeis4.)