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%I #20 Sep 08 2022 08:45:17
%S 7,29,41,79,119,137,143,169,187,241,259,263,281,307,313,319,341,361,
%T 377,403,427,439,449,461,467,493,547,553,557,587,673,689,701,703,719,
%U 721,731,781,791,847,887,901,911,931,943,979,1027,1073,1093,1097,1103,1207,1219,1229,1307,1327,1331
%N Numbers k such that the string 101001000k is prime.
%H Daniel Starodubtsev, <a href="/A103603/b103603.txt">Table of n, a(n) for n = 1..10000</a>
%e If k=7, then 101001000k = 1010010007 (prime).
%e If k=41, then 101001000k = 10100100041 (prime).
%e If k=119, then 101001000k = 101001000119 (prime).
%t Select[Range[1500],PrimeQ[FromDigits[Join[{1,0,1,0,0,1,0,0,0}, IntegerDigits[ #]]]]&] (* _Harvey P. Dale_, Jul 12 2011 *)
%t Select[Range[2000],PrimeQ[101001000*10^IntegerLength[#]+#]&] (* _Harvey P. Dale_, Jan 16 2020 *)
%o (Magma) [ n: n in [1..1750] | IsPrime(Seqint(Intseq(n) cat [0, 0, 0, 1, 0, 0, 1, 0, 1])) ]; // _Vincenzo Librandi_, Feb 02 2011
%K base,nonn
%O 1,1
%A _Parthasarathy Nambi_, Mar 23 2005