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A023272
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Numbers n such that n remains prime through 3 iterations of function f(x) = 2x + 1.
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34
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2, 5, 89, 179, 359, 509, 1229, 1409, 2699, 3539, 6449, 10589, 11549, 11909, 12119, 17159, 19709, 19889, 22349, 26189, 27479, 30389, 43649, 53639, 53849, 55229, 57839, 60149, 61409, 63419, 66749, 71399, 74699, 75329, 82499, 87539, 98369, 101399, 104369
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| n, 2*n+1, 4*n+3 and 8*n+7 are primes. [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 04 2010]
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LINKS
| Nathaniel Johnston, Table of n, a(n) for n = 1..1000
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MAPLE
| p:=2: for n from 1 to 5000 do if(isprime(2*p+1) and isprime(4*p+3) and isprime(8*p+7))then printf("%d, ", p): fi: p:=nextprime(p): od: # Nathaniel Johnston, Jun 30 2011
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MATHEMATICA
| Select[Prime[Range[10^3*4]], PrimeQ[a1=2*#+1]&&PrimeQ[a2=2*a1+1]&&PrimeQ[a3=2*a2+1] &] (from Vladimir Orlovsky (4vladimir(AT)gmail.com), May 01 2008)
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PROG
| (MAGMA) [n: n in [1..100000] | IsPrime(n) and IsPrime(2*n+1) and IsPrime(4*n+3) and IsPrime(8*n+7)] [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Aug 04 2010]
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CROSSREFS
| Cf. (A005384 and A005385), A007700, A023302, A023330, A057331, A005602.
Sequence in context: A120798 A048187 A082431 * A057978 A093308 A162569
Adjacent sequences: A023269 A023270 A023271 * A023273 A023274 A023275
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KEYWORD
| nonn
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AUTHOR
| David W. Wilson (davidwwilson(AT)comcast.net)
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