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A023266
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Numbers n such that n remains prime through 2 iterations of function f(x) = 9x + 4.
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0
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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; internal format)
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OFFSET
| 1,1
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COMMENTS
| n, 9*n+4 and 81*n+40 are primes. [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 04 2010]
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PROG
| (MAGMA) [n: n in [1..100000] | IsPrime(n) and IsPrime(9*n+4) and IsPrime(81*n+40)] [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 04 2010]
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CROSSREFS
| Sequence in context: A053648 A138862 A080173 * A110581 A128436 A034915
Adjacent sequences: A023263 A023264 A023265 * A023267 A023268 A023269
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KEYWORD
| nonn
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AUTHOR
| David W. Wilson (davidwwilson(AT)comcast.net)
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