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A118479
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Least n-digit prime which is also a twin prime and Sophie Germain prime.
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2
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3, 11, 179, 1019, 10091, 100361, 1000211, 10001399, 100001651, 1000002359, 10000003001, 100000026569, 1000000000061, 10000000019759, 100000000018109, 1000000000029911, 10000000000013741, 100000000000004381
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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EXAMPLE
| 3 and 5 twin primes and 2*3+1=7 prime, so 3 is first of twin primes and Sophie Germain prime, least prime like this of one digit, so a(1)=3
11 and 13 twin primes ans 2*11+1=23 prime, so 11 first of twin primes and Sophie Germain prime, least prime like this with two digits, so a(2)=11
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MATHEMATICA
| f[n_] := Block[{k = 10^(n - 1)}, While[ !PrimeQ[k] || !PrimeQ[k + 2] || !PrimeQ[2k + 1], k++ ]; k]; Array[f, 18] (* Robert G. Wilson v *)
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CROSSREFS
| Sequence in context: A006485 A003115 A053888 * A103836 A081484 A125738
Adjacent sequences: A118476 A118477 A118478 * A118480 A118481 A118482
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KEYWORD
| nonn
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AUTHOR
| Pierre CAMI (pierre-cami(AT)bbox.fr), May 05 2006
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EXTENSIONS
| Edited by Robert G. Wilson v (rgwv(at)rgwv.com), May 13 2006
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