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 A103603 Numbers k such that the string 101001000k is prime. 4
 7, 29, 41, 79, 119, 137, 143, 169, 187, 241, 259, 263, 281, 307, 313, 319, 341, 361, 377, 403, 427, 439, 449, 461, 467, 493, 547, 553, 557, 587, 673, 689, 701, 703, 719, 721, 731, 781, 791, 847, 887, 901, 911, 931, 943, 979, 1027, 1073, 1093, 1097, 1103, 1207, 1219, 1229, 1307, 1327, 1331 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS Daniel Starodubtsev, Table of n, a(n) for n = 1..10000 EXAMPLE If k=7, then 101001000k = 1010010007 (prime). If k=41, then 101001000k = 10100100041 (prime). If k=119, then 101001000k = 101001000119 (prime). MATHEMATICA Select[Range[1500], PrimeQ[FromDigits[Join[{1, 0, 1, 0, 0, 1, 0, 0, 0}, IntegerDigits[ #]]]]&] (* Harvey P. Dale, Jul 12 2011 *) Select[Range[2000], PrimeQ[101001000*10^IntegerLength[#]+#]&] (* Harvey P. Dale, Jan 16 2020 *) PROG (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 CROSSREFS Sequence in context: A155476 A166970 A075583 * A045465 A330723 A165492 Adjacent sequences: A103600 A103601 A103602 * A103604 A103605 A103606 KEYWORD base,nonn AUTHOR Parthasarathy Nambi, Mar 23 2005 STATUS approved

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Last modified January 27 05:57 EST 2023. Contains 359837 sequences. (Running on oeis4.)