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 A023329 Numbers n such that n remains prime through 4 iterations of function f(x) = 10x + 9. 1
 13, 139, 293, 1889, 2939, 3719, 6089, 7741, 12823, 19753, 21391, 22861, 28513, 36721, 37967, 40949, 60899, 76519, 83621, 101747, 121687, 127549, 128239, 142099, 149197, 153817, 155581, 158489, 160159, 169283, 173651, 180749, 185831, 192037, 198221 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS n, 10*n+9, 100*n+99, 1000*n+999 and 10000*n+9999 are primes. - Vincenzo Librandi, Aug 04 2010 LINKS John Cerkan, Table of n, a(n) for n = 1..10000 FORMULA a(n) == 9 or 13 (mod 14). - John Cerkan, Oct 09 2016 PROG (MAGMA) [n: n in [1..5000000] | IsPrime(n) and IsPrime(10*n+9) and IsPrime(100*n+99) and IsPrime(1000*n+999) and IsPrime(10000*n+9999)] // Vincenzo Librandi, Aug 04 2010 CROSSREFS Subsequence of A023240, A023270, A023301, and A102700. Sequence in context: A088096 A271069 A023301 * A280745 A142896 A193700 Adjacent sequences:  A023326 A023327 A023328 * A023330 A023331 A023332 KEYWORD nonn AUTHOR STATUS approved

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Last modified August 23 22:45 EDT 2019. Contains 326254 sequences. (Running on oeis4.)