A108112 - OEIS

%I #12 Sep 08 2022 08:45:19

%S 29,31,37,41,43,67,71,79,89,103,121,169,193,199,209,221,223,253,257,

%T 263,271,289,323,383,391,421,431,439,443,461,463,487,517,521,523,557,

%U 559,601,611,613,617,619,629,641,677,689,691,701,733,757,769,781,787,799,803,811,821,827,839,859

%N Numbers k such that the string 3129k is prime.

%H Harvey P. Dale, <a href="/A108112/b108112.txt">Table of n, a(n) for n = 1..1000</a>

%e k=29 is in the sequence because 3129k = 312929 is prime.

%e k=103 is in the sequence because 3129k = 3129103 is prime.

%t Select[Range[1000],PrimeQ[3129*10^IntegerLength[#]+#]&] (* _Harvey P. Dale_, Jan 14 2015 *)

%o (Magma) [ n: n in [1..1750] | IsPrime(Seqint(Intseq(n) cat [9, 2, 1, 3])) ]; // _Vincenzo Librandi_, Feb 02 2011

%K nonn,base

%O 1,1

%A _Parthasarathy Nambi_, Jun 25 2005