A110677 - OEIS

%I #13 Sep 08 2022 08:45:20

%S 1,23,31,37,41,49,67,83,97,103,119,131,133,163,199,203,217,221,233,

%T 251,257,263,277,283,301,307,311,313,331,373,383,391,397,401,419,427,

%U 431,433,439,469,481,497,509,511,527,593,601,611,619,641

%N Numbers k such that the string 3333k is prime.

%H Vincenzo Librandi, <a href="/A110677/b110677.txt">Table of n, a(n) for n = 1..2500</a>

%e k=103 is in the sequence because  3333k = 3333103 is prime.

%t Select[Range[700], PrimeQ[FromDigits[Join[{3, 3, 3, 3}, IntegerDigits[#]]]] &] (* _Vincenzo Librandi_, Feb 03 2017 *)

%o (Magma) [n: n in [1..700] | IsPrime(Seqint(Intseq(n) cat [3,3,3,3]))]; // _Vincenzo Librandi_, Feb 03 2017

%K nonn,base

%O 1,2

%A _Parthasarathy Nambi_, Sep 14 2005