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 A023266 Numbers n such that n remains prime through 2 iterations of function f(x) = 9x + 4. 4
 3, 7, 31, 37, 41, 71, 73, 83, 107, 191, 283, 307, 317, 337, 373, 421, 631, 743, 773, 821, 857, 883, 967, 1283, 1297, 1361, 1451, 1567, 1571, 1637, 1823, 1973, 2137, 2207, 2351, 2417, 2677, 2683, 2837, 3011, 3083, 3271, 3331, 3517, 3571, 3691, 3727, 3793, 3877 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS n, 9*n+4 and 81*n+40 are primes. - Vincenzo Librandi, Aug 04 2010 LINKS Harvey P. Dale, Table of n, a(n) for n = 1..10000 MATHEMATICA Select[Prime[Range[600]], AllTrue[Rest[NestList[9#+4&, #, 2]], PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Jul 15 2016 *) PROG (MAGMA) [n: n in [1..100000] | IsPrime(n) and IsPrime(9*n+4) and IsPrime(81*n+40)] // Vincenzo Librandi, Aug 04 2010 CROSSREFS Sequence in context: A053648 A138862 A080173 * A217198 A110581 A128436 Adjacent sequences:  A023263 A023264 A023265 * A023267 A023268 A023269 KEYWORD nonn AUTHOR STATUS approved

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Last modified October 23 21:57 EDT 2019. Contains 328373 sequences. (Running on oeis4.)