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 A023301 Numbers n such that n remains prime through 3 iterations of function f(x) = 10x + 9. 3
 13, 139, 293, 331, 547, 967, 1049, 1399, 1567, 1889, 1997, 2087, 2137, 2309, 2423, 2437, 2753, 2939, 3719, 3761, 3919, 4451, 4517, 4621, 6089, 7001, 7741, 8423, 8849, 9437, 10487, 11657, 12007, 12347, 12823, 13469, 15289, 15373, 15661, 17737, 17989 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS n, 10*n+9, 100*n+99 and 1000*n+999 are primes. - Vincenzo Librandi, Aug 04 2010 LINKS John Cerkan, Table of n, a(n) for n = 1..10000 MATHEMATICA nrp3Q[n_]:=AllTrue[Rest[NestList[10#+9&, n, 3]], PrimeQ]; Select[Prime[ Range[ 2100]], nrp3Q] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Aug 12 2019 *) PROG (MAGMA) [n: n in [1..450000] | IsPrime(n) and IsPrime(10*n+9) and IsPrime(100*n+99) and IsPrime(1000*n+999)] // Vincenzo Librandi, Aug 04 2010 CROSSREFS Subsequence of A023240, A023270, and A102700. Sequence in context: A090505 A088096 A271069 * A023329 A280745 A142896 Adjacent sequences:  A023298 A023299 A023300 * A023302 A023303 A023304 KEYWORD nonn AUTHOR STATUS approved

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Last modified September 21 22:17 EDT 2019. Contains 327284 sequences. (Running on oeis4.)