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Numbers k such that k111111 is prime.
2

%I #21 Nov 30 2022 18:07:06

%S 29,34,61,71,80,85,89,94,101,103,106,107,115,118,122,124,128,131,149,

%T 158,163,166,193,194,199,205,212,233,248,251,256,265,268,277,290,316,

%U 323,326,328,346,347,355,356,361,365,367,382,383,386,389,394,398,404,424,430,431,436,439,452,454,457

%N Numbers k such that k111111 is prime.

%H Daniel Starodubtsev, <a href="/A102527/b102527.txt">Table of n, a(n) for n = 1..10000</a>

%e If k=29, then k111111 = 29111111 (prime).

%e If k=101, then k111111 = 101111111 (prime).

%e If k=122, then k111111 = 122111111 (prime).

%t Select[Range[500],PrimeQ[FromDigits[Join[IntegerDigits[#],{1,1,1,1,1,1} ]]]&] (* _Harvey P. Dale_, Aug 22 2011 *)

%t Select[Range[500],PrimeQ[#*10^6+111111]&] (* _Harvey P. Dale_, Nov 30 2022 *)

%o (Magma) [ n: n in [1..700] | IsPrime(Seqint([1,1,1,1,1,1] cat Intseq(n))) ]; // _Vincenzo Librandi_, Feb 04 2011

%K base,nonn

%O 1,1

%A _Parthasarathy Nambi_, Feb 24 2005