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A023301
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Numbers n such that n remains prime through 3 iterations of function f(x) = 10x + 9.
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1
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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; internal format)
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OFFSET
| 1,1
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COMMENTS
| n, 10*n+9, 100*n+99 and 1000*n+999 are primes. [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 04 2010]
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PROG
| (MAGMA) [n: n in [1..450000] | IsPrime(n) and IsPrime(10*n+9) and IsPrime(100*n+99) and IsPrime(1000*n+999)] [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 04 2010]
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CROSSREFS
| Sequence in context: A113579 A090505 A088096 * A023329 A142896 A193700
Adjacent sequences: A023298 A023299 A023300 * A023302 A023303 A023304
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KEYWORD
| nonn
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AUTHOR
| David W. Wilson (davidwwilson(AT)comcast.net)
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