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A109357 Numbers k such that the string 112354k is prime. 1

%I

%S 1,21,73,81,127,157,159,181,211,213,217,259,267,271,273,283,289,301,

%T 303,321,327,337,369,409,423,457,477,507,523,537,553,559,597,603,621,

%U 631,651,691,699,727,799,807,817,843,849,867,877,897,909,919,927,967,969,981,993,997,1017,1021,1047

%N Numbers k such that the string 112354k is prime.

%H Michael De Vlieger, <a href="/A109357/b109357.txt">Table of n, a(n) for n = 1..10000</a>

%e If k=1 then 112354k = 1123541 (prime).

%e If k=213 then 112354k = 112354213 (prime).

%t Select[Range[1050], PrimeQ[112354*10^IntegerLength[#] + #] &] (* _Michael De Vlieger_, Jan 22 2018 *)

%o (MAGMA) [ n: n in [1..1750] | IsPrime(Seqint(Intseq(n) cat [4, 5, 3, 2, 1, 1])) ]; // _Vincenzo Librandi_, Feb 02 2011

%K nonn,base

%O 1,2

%A _Parthasarathy Nambi_, Aug 22 2005

%E More terms from _Vincenzo Librandi_, Feb 02 2011

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Last modified October 17 15:40 EDT 2021. Contains 348064 sequences. (Running on oeis4.)