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A112041
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Numbers n such that 1*n+1, 3*n+1, 9*n+1, 27*n+1 are all primes.
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2
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4, 60, 180, 760, 910, 1020, 1230, 1600, 1860, 2160, 2280, 2440, 3850, 5800, 7320, 8680, 12940, 13780, 14740, 17350, 17400, 21840, 22720, 22960, 26040, 27010, 31050, 33870, 34060, 35200, 39900, 40030, 44350, 45280, 45540, 45750, 50460, 52050
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| 1*4+1=5
3*4+1=13
9*4+1=37
27*4+1=109; 5,13,37,109 are all prime so k(1)=4
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PROG
| (MAGMA) [n: n in [1..100000] |IsPrime(n+1) and IsPrime(3*n+1) and IsPrime(9*n+1) and IsPrime(27*n+1)] [From Vincenzo Librandi (vincenzo.librandi(AT)tin.it), Nov 13 2010]
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CROSSREFS
| Cf. A112042, A112043.
Sequence in context: A058173 A074835 A060492 * A002060 A007220 A034866
Adjacent sequences: A112038 A112039 A112040 * A112042 A112043 A112044
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KEYWORD
| nonn
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AUTHOR
| Pierre CAMI (pierre-cami(AT)bbox.fr), Aug 26 2005
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