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A023208
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Numbers n such that n and 3n + 2 both prime.
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30
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3, 5, 7, 13, 17, 19, 23, 29, 37, 43, 59, 79, 83, 89, 97, 103, 127, 139, 149, 163, 167, 173, 197, 199, 227, 233, 239, 257, 269, 293, 313, 317, 337, 349, 353, 367, 383, 397, 409, 419, 433, 439, 457, 479, 499, 503, 523, 569, 577, 607, 643, 659, 709, 757, 769, 797, 859, 863
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| Also, son primes of order 1. For smallest son primes of order n see A136027 (also definition). For son primes of order 2 see A136082 - Artur Jasinski, Dec 12 2007
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LINKS
| Zak Seidov, Table of n, a(n) for n = 1..1000
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MATHEMATICA
| n = 1; a = {}; Do[If[PrimeQ[(Prime[k] - 2n)/(2n + 1)], AppendTo[a, (Prime[k] - 2n)/(2n + 1)]], {k, 1, 1000}]; a - Artur Jasinski, Dec 12 2007
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PROG
| (PARI) isA023208(n) = isprime(n) && isprime(3*n+2) [From Michael B. Porter, Jan 30 2010]
(MAGMA) [n: n in [0..1000] | IsPrime(n) and IsPrime(3*n+2)] [From V. Librandi, Nov 20 2010]
(Haskell)
a023208 n = a023208_list !! (n-1)
a023208_list = filter ((== 1) . a010051 . (+ 2) . (* 3)) a000040_list
-- Reinhard Zumkeller, Aug 15 2011
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CROSSREFS
| Cf. A023208, A094524, A136019, A136020, A136026, A136027, A136082, A136083, A136084, A136085, A136086, A136087, A136088, A136089, A136090, A136091.
Sequence in context: A031163 A106119 A152820 * A162358 A154320 A173912
Adjacent sequences: A023205 A023206 A023207 * A023209 A023210 A023211
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KEYWORD
| nonn
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AUTHOR
| David W. Wilson (davidwwilson(AT)comcast.net)
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EXTENSIONS
| Edited by N. J. A. Sloane (njas(AT)research.att.com), May 16 2008 at the suggestion of R. J. Mathar
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