A108111 - OEIS

%I #14 Sep 08 2022 08:45:19

%S 1,23,29,47,49,73,77,79,101,113,127,151,161,167,193,197,209,211,217,

%T 221,223,241,289,307,319,413,421,427,433,443,457,493,503,527,553,569,

%U 583,587,619,629,637,647,653,671,683,707,713,739

%N Numbers k such that the string 2931k is prime.

%e k=1 is in the sequence because 2931k = 29311 is a prime number.

%e k=113 is in the sequence because 2931k = 2931113 is a prime number.

%t Select[Range[1000],PrimeQ[#+2931 10^IntegerLength[#]]&] (* _Harvey P. Dale_, Sep 16 2011 *)

%o (Magma) [ n: n in [1..750] | IsPrime(Seqint(Intseq(n) cat [1, 3, 9, 2])) ]; // _Vincenzo Librandi_, Feb 02 2011

%K nonn,base

%O 1,2

%A _Parthasarathy Nambi_, Jun 25 2005