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A023270
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Numbers n such that n remains prime through 2 iterations of function f(x) = 10x + 9.
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0
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5, 13, 19, 23, 47, 61, 103, 127, 139, 233, 257, 293, 331, 433, 463, 491, 499, 547, 593, 701, 859, 967, 1009, 1013, 1049, 1223, 1321, 1399, 1493, 1567, 1723, 1811, 1867, 1889, 1997, 2039, 2063, 2087, 2137, 2203, 2267, 2273, 2309, 2423, 2437, 2441, 2609, 2633
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| n, 10*n+9 and 100*n+99 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(10*n+9) and IsPrime(100*n+99)] [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 04 2010]
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CROSSREFS
| Sequence in context: A171603 A118915 A084442 * A103804 A129919 A045454
Adjacent sequences: A023267 A023268 A023269 * A023271 A023272 A023273
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KEYWORD
| nonn
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AUTHOR
| David W. Wilson (davidwwilson(AT)comcast.net)
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