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A102249 Numbers k such that k1111 is prime. 2

%I

%S 10,13,31,36,51,57,61,69,72,78,79,90,91,97,117,120,127,129,135,138,

%T 153,156,166,174,183,184,189,201,205,210,222,225,226,234,237,240,241,

%U 244,252,261,265,273,276,280,285,292,304,306,309,318,322,325,327,337,345

%N Numbers k such that k1111 is prime.

%H Daniel Starodubtsev, <a href="/A102249/b102249.txt">Table of n, a(n) for n = 1..10000</a>

%e At k=10, k1111 = 101111 (prime).

%e At k=90, k1111 = 901111 (prime).

%e At k=138, k1111 = 1381111 (prime).

%t Select[ Range[ 350], PrimeQ[ FromDigits[ Flatten[ IntegerDigits /@ { #, 1, 1, 1, 1}]]] &] (* _Robert G. Wilson v_, Feb 21 2005 *)

%t Select[Range[400],PrimeQ[#*10^4+1111]&] (* _Harvey P. Dale_, Jul 14 2019 *)

%Y Cf. A024912.

%K nonn,base

%O 1,1

%A _Parthasarathy Nambi_, Feb 18 2005

%E More terms from _Robert G. Wilson v_, Feb 21 2005

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Last modified January 29 23:01 EST 2023. Contains 359939 sequences. (Running on oeis4.)